Editor: Add code syntax highlighting

[dennyluan]

Please Describe The Problem To Be Solved Prosemirror supports code highlighting. We plan to add this support to our editor.

We can either use CodeMirror or explore some other ways to support inline code highlighting. Ideally we can add many flavors of highlighting as well.

Here's a simple mockup of the code block.

[cindywu]

https://linear.app/issue/JEL-24/add-code-syntax-highlighting-to-editor