CKEditor CodeMirror Plugin

# Source Area

The CodeMirror plugin extends the source area of the framed CKEditor, with the source area you can edit the raw HTML content of an editor with Syntax Highlighting.

To enable this plugin, basically add `extraPlugins: 'codemirror'` to editor's config:

    // Framed editor.
    CKEDITOR.replace( 'textarea_id', {
                    extraPlugins: 'codemirror'
    });

Framed editor: <!-- write some xml below -->