While CodeMirror is extremely helpful for regular wiki editing tools, it has no means for third-party usage outside of `#wpTextbox1`:
https://github.com/wikimedia/mediawiki-extensions-CodeMirror/blob/master/resources/ext.CodeMirror.js
I think making the code more agnostic and exposing the function for enabling CodeMirror in any other libraries working with WikiEditor, for example, #convenient-discussions, will be beneficial for them.
**Acceptance criteria**
* CodeMirror should be usable on any textarea
To test, you can go to Special:BlankPage and enter the following in your JS console:
```lang=javascript
$( '.mw-body-content' ).append( $('<textarea>' ) );
mw.loader.using( [ 'ext.CodeMirror.v6', 'ext.CodeMirror.v6.mode.mediawiki' ] ).then( ( require ) => {
const CodeMirror = require( 'ext.CodeMirror.v6' );
const mediawikiLang = require( 'ext.CodeMirror.v6.mode.mediawiki' );
const cm = new CodeMirror( $( 'textarea' ) );
cm.initialize( [ cm.defaultExtensions, mediawikiLang() ] );
} );
```