feat: code block tab (#1063)

* Try to find a way to recognize the codeblock tabs, its title, and
where it ends
- I try using DOCUSAURUS_CODE_TABS to mark the start
- Use TAB_TITLE to mark the title of the tab
- END_TAB to mark the end of that tab
- END_DOCUSAURUS_CODE_TABS to mark the end of the whole code blocks
then parse using regex and render accordingly

* Added on click hook

* Added example on how to write it, how to use it, how it will look like can be reverted later

* Fix css error

* - Move addEventListener part to lib/static
- Remove comments

* Add documentation

* Remove examples

* Change syntax of the codetabs

v1/lib/core/Head.js

@@ -188,6 +188,7 @@ class Head extends React.Component {
           rel="stylesheet"
           href={`${this.props.config.baseUrl}css/main.css`}
         />
+        <script src={`${this.props.config.baseUrl}js/codetabs.js`} />
       </head>
     );
   }