Basic Chat Features

[gleachkr]

For 0.1.0, we should try to get the basic matrix chat features that would be most relevant for social annotation.

• [x] Editing sent messages
• [x] LaTeX, via KaTeX
• [x] Rich Text, via commonmark markdown
• [x] Message redaction/deletion
• [x] ~Kick/ban by moderators and room owners~ (initial beta will assume trust)
• [x] ~Fira Logic font~ (postpone for a larger issue handling code-blocks)
• [x] Replies

Some less relevant features are

1. Media uploads (images, videos, voice messages)
2. File uploads
3. Emotes
4. Mentions
5. Display join and leave events
6. Read receipts
7. Pinned messages

But maybe these should be added later.