code highlighting

[pngwn]

beepboop.

Look into highlighting inline code too (#543)

Issues to address:

• [ ] #554
• [ ] #548
• [ ] #543
• [ ] #514
• [ ] #486
• [ ] #458
• [ ] #392
• [ ] #304
• [ ] #212
• [ ] #139
• [ ] #52 (maybe unrelated)
• [ ] #310
• [ ] #431