[Feature] Add source mode to editor

[kevin8999]

Problem

When users want to write a guide, they are forced to use the prettified "live preview mode". This mode forces users who know Markdown to use a (currently) buggy editor.

Proposal

Enable source mode in MDXEditor so users can write in raw Markdown.

More information can be viewed here: https://mdxeditor.dev/editor/docs/diff-source

Area

app (frontend)

Confirmations

• I searched existing issues and this is not a duplicate.

[kevin8999]

If there is a good-first-issue tag, I would recommend adding it here. This feature seems relatively straightforward to implement.