feature #3909 Update the CssSelector component documentation (stof)

This PR was merged into the 2.3 branch.

Discussion
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Update the CssSelector component documentation

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all (or 2.3+)
| Fixed tickets | n/a

This updates the CssSelector component for changes done in Symfony 2.3. The rewritten component supports more pseudo-classes

Commits
-------

7db0c58 Update the CssSelector component documentation

Author: weaverryan

components/css_selector.rst

@@ -55,7 +55,7 @@ This gives the following output:
 
 .. code-block:: text
 
-    descendant-or-self::div[contains(concat(' ',normalize-space(@class), ' '), ' item ')]/h4/a
+    descendant-or-self::div[@class and contains(concat(' ',normalize-space(@class), ' '), ' item ')]/h4/a
 
 You can use this expression with, for instance, :phpclass:`DOMXPath` or
 :phpclass:`SimpleXMLElement` to find elements in a document.
@@ -76,17 +76,15 @@ web-browser.
 
 * link-state selectors: ``:link``, ``:visited``, ``:target``
 * selectors based on user action: ``:hover``, ``:focus``, ``:active``
-* UI-state selectors: ``:enabled``, ``:disabled``, ``:indeterminate``
-  (however, ``:checked`` and ``:unchecked`` are available)
+* UI-state selectors: ``:invalid``, ``:indeterminate`` (however, ``:enabled``, 
+  ``:disabled``, ``:checked`` and ``:unchecked`` are available)
 
 Pseudo-elements (``:before``, ``:after``, ``:first-line``,
 ``:first-letter``) are not supported because they select portions of text
 rather than elements.
 
 Several pseudo-classes are not yet supported:
 
-* ``:lang(language)``
-* ``root``
 * ``*:first-of-type``, ``*:last-of-type``, ``*:nth-of-type``,
   ``*:nth-last-of-type``, ``*:only-of-type``. (These work with an element
   name (e.g. ``li:first-of-type``) but not with ``*``.