Plugins documentation (#92)

* feat: added first draft on plugins

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* Update src/guide/plugins.md

Co-authored-by: Rahul Kadyan <hi@znck.me>

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* Update src/guide/plugins.md

Co-authored-by: Ben Hong <ben@bencodezen.io>

* fix: removed global methos

* fix: added parantheses to methods

Co-authored-by: Ben Hong <ben@bencodezen.io>
Co-authored-by: Rahul Kadyan <hi@znck.me>

Author: 3 people

src/.vuepress/config.js

@@ -45,7 +45,8 @@ const sidebar = {
       children: [
         '/guide/mixins',
         '/guide/custom-directive',
-        '/guide/render-function'
+        '/guide/render-function',
+        '/guide/plugins'
       ]
     },
     {

src/guide/plugins.md

@@ -0,0 +1,65 @@
+# Plugins
+
+Plugins usually add global-level functionality to Vue. There is no strictly defined scope for a plugin, but common scenarios where plugins are useful include:
+
+1. Add some global methods or properties, e.g. [vue-custom-element](https://github.com/karol-f/vue-custom-element).
+
+2. Add one or more global assets: directives/filters/transitions etc. (e.g. [vue-touch](https://github.com/vuejs/vue-touch)).
+
+3. Add some component options by global mixin (e.g. [vue-router](https://github.com/vuejs/vue-router)).
+
+4. Add some Vue instance methods by attaching them to `config.globalProperties`.
+
+5. A library that provides an API of its own, while at the same time injecting some combination of the above (e.g. [vue-router](https://github.com/vuejs/vue-router)).
+
+## Using a Plugin
+
+After a Vue app has been initialized with `createApp()`, you can add a plugin to your application by calling the `use()` method:
+
+```js
+// calls `MyPlugin.install(Vue)`
+const app = Vue.createApp({})
+app.use(MyPlugin)
+```
+
+If you need to define configuration for a plugin, you can pass a config object as the second argument:
+
+```js
+app.use(MyPlugin, { someOption: true })
+```
+
+`app.use()` automatically prevents you from using the same plugin more than once, so calling it multiple times on the same plugin will install the plugin only once.
+
+Checkout [awesome-vue](https://github.com/vuejs/awesome-vue#components--libraries) for a huge collection of community-contributed plugins and libraries.
+
+## Writing a Plugin
+
+A Vue.js plugin should expose an `install()` method. The method will be called with the application instance as the first argument, along with possible options:
+
+```js
+MyPlugin.install = (app, options) => {
+  // 1. add a global provided function/attribute (this would require using an 'inject' in components where we want to access 'myProvidedAttribute')
+  app.provide('myProvidedAttribute', 'foo')
+
+  // 2. add an instance method (this will be available in every component)
+  app.config.globalProperties.$myMethod = (methodOptions) => {
+    // some logic ...
+  }
+
+  // 3. add a global asset
+  app.directive('my-directive', {
+    bind (el, binding, vnode, oldVnode) {
+      // some logic ...
+    }
+    ...
+  })
+
+  // 4. inject some component options
+  app.mixin({
+    created() {
+      // some logic ...
+    }
+    ...
+  })
+}
+```