docs(ngShowHide): use backticks to denote CSS classes and directive names

add backticks around directive names to improve documentation consistency, as it's used in some
parts of the docs already.

Closes angular#9081

Author: petebacondarwin

src/ng/directive/ngShowHide.js

@@ -6,8 +6,8 @@
  *
  * @description
  * The `ngShow` directive shows or hides the given HTML element based on the expression
- * provided to the ngShow attribute. The element is shown or hidden by removing or adding
- * the `ng-hide` CSS class onto the element. The `.ng-hide` CSS class is predefined
+ * provided to the `ngShow` attribute. The element is shown or hidden by removing or adding
+ * the `.ng-hide` CSS class onto the element. The `.ng-hide` CSS class is predefined
  * in AngularJS and sets the display style to none (using an !important flag).
  * For CSP mode please add `angular-csp.css` to your html file (see {@link ng.directive:ngCsp ngCsp}).
  *
@@ -19,8 +19,8 @@
  * <div ng-show="myValue" class="ng-hide"></div>
  * ```
  *
- * When the ngShow expression evaluates to false then the ng-hide CSS class is added to the class attribute
- * on the element causing it to become hidden. When true, the ng-hide CSS class is removed
+ * When the `ngShow` expression evaluates to false then the `.ng-hide` CSS class is added to the class attribute
+ * on the element causing it to become hidden. When true, the `.ng-hide` CSS class is removed
  * from the element causing the element not to appear hidden.
  *
  * <div class="alert alert-warning">
@@ -30,7 +30,7 @@
  *
  * ## Why is !important used?
  *
- * You may be wondering why !important is used for the .ng-hide CSS class. This is because the `.ng-hide` selector
+ * You may be wondering why !important is used for the `.ng-hide` CSS class. This is because the `.ng-hide` selector
  * can be easily overridden by heavier selectors. For example, something as simple
  * as changing the display style on a HTML list item would make hidden elements appear visible.
  * This also becomes a bigger issue when dealing with CSS frameworks.
@@ -39,7 +39,7 @@
  * specificity (when !important isn't used with any conflicting styles). If a developer chooses to override the
  * styling to change how to hide an element then it is just a matter of using !important in their own CSS code.
  *
- * ### Overriding .ng-hide
+ * ### Overriding `.ng-hide`
  *
  * By default, the `.ng-hide` class will style the element with `display:none!important`. If you wish to change
  * the hide behavior with ngShow/ngHide then this can be achieved by restating the styles for the `.ng-hide`
@@ -57,7 +57,7 @@
  *
  * By default you don't need to override in CSS anything and the animations will work around the display style.
  *
- * ## A note about animations with ngShow
+ * ## A note about animations with `ngShow`
  *
  * Animations in ngShow/ngHide work with the show and hide events that are triggered when the directive expression
  * is true and false. This system works like the animation system present with ngClass except that
@@ -82,8 +82,8 @@
  * property to block during animation states--ngAnimate will handle the style toggling automatically for you.
  *
  * @animations
- * addClass: .ng-hide - happens after the ngShow expression evaluates to a truthy value and the just before contents are set to visible
- * removeClass: .ng-hide - happens after the ngShow expression evaluates to a non truthy value and just before the contents are set to hidden
+ * addClass: `.ng-hide` - happens after the `ngShow` expression evaluates to a truthy value and the just before contents are set to visible
+ * removeClass: `.ng-hide` - happens after the `ngShow` expression evaluates to a non truthy value and just before the contents are set to hidden
  *
  * @element ANY
  * @param {expression} ngShow If the {@link guide/expression expression} is truthy
@@ -163,7 +163,7 @@ var ngShowDirective = ['$animate', function($animate) {
  *
  * @description
  * The `ngHide` directive shows or hides the given HTML element based on the expression
- * provided to the ngHide attribute. The element is shown or hidden by removing or adding
+ * provided to the `ngHide` attribute. The element is shown or hidden by removing or adding
  * the `ng-hide` CSS class onto the element. The `.ng-hide` CSS class is predefined
  * in AngularJS and sets the display style to none (using an !important flag).
  * For CSP mode please add `angular-csp.css` to your html file (see {@link ng.directive:ngCsp ngCsp}).
@@ -176,8 +176,8 @@ var ngShowDirective = ['$animate', function($animate) {
  * <div ng-hide="myValue"></div>
  * ```
  *
- * When the ngHide expression evaluates to true then the .ng-hide CSS class is added to the class attribute
- * on the element causing it to become hidden. When false, the ng-hide CSS class is removed
+ * When the `.ngHide` expression evaluates to true then the `.ng-hide` CSS class is added to the class attribute
+ * on the element causing it to become hidden. When false, the `.ng-hide` CSS class is removed
  * from the element causing the element not to appear hidden.
  *
  * <div class="alert alert-warning">
@@ -187,7 +187,7 @@ var ngShowDirective = ['$animate', function($animate) {
  *
  * ## Why is !important used?
  *
- * You may be wondering why !important is used for the .ng-hide CSS class. This is because the `.ng-hide` selector
+ * You may be wondering why !important is used for the `.ng-hide` CSS class. This is because the `.ng-hide` selector
  * can be easily overridden by heavier selectors. For example, something as simple
  * as changing the display style on a HTML list item would make hidden elements appear visible.
  * This also becomes a bigger issue when dealing with CSS frameworks.
@@ -196,7 +196,7 @@ var ngShowDirective = ['$animate', function($animate) {
  * specificity (when !important isn't used with any conflicting styles). If a developer chooses to override the
  * styling to change how to hide an element then it is just a matter of using !important in their own CSS code.
  *
- * ### Overriding .ng-hide
+ * ### Overriding `.ng-hide`
  *
  * By default, the `.ng-hide` class will style the element with `display:none!important`. If you wish to change
  * the hide behavior with ngShow/ngHide then this can be achieved by restating the styles for the `.ng-hide`
@@ -214,7 +214,7 @@ var ngShowDirective = ['$animate', function($animate) {
  *
  * By default you don't need to override in CSS anything and the animations will work around the display style.
  *
- * ## A note about animations with ngHide
+ * ## A note about animations with `ngHide`
  *
  * Animations in ngShow/ngHide work with the show and hide events that are triggered when the directive expression
  * is true and false. This system works like the animation system present with ngClass, except that the `.ng-hide`
@@ -238,8 +238,8 @@ var ngShowDirective = ['$animate', function($animate) {
  * property to block during animation states--ngAnimate will handle the style toggling automatically for you.
  *
  * @animations
- * removeClass: .ng-hide - happens after the ngHide expression evaluates to a truthy value and just before the contents are set to hidden
- * addClass: .ng-hide - happens after the ngHide expression evaluates to a non truthy value and just before the contents are set to visible
+ * removeClass: `.ng-hide` - happens after the `ngHide` expression evaluates to a truthy value and just before the contents are set to hidden
+ * addClass: `.ng-hide` - happens after the `ngHide` expression evaluates to a non truthy value and just before the contents are set to visible
  *
  * @element ANY
  * @param {expression} ngHide If the {@link guide/expression expression} is truthy then