Add drafts for posts and comments

[micahmo]

Pull Request Description

This PR introduces drafts for posts and comments. Drafts are saved upon exiting the edit screen (without posting) and on a timer (in case the app is quit/crashes). They are saved per community or post/comment.

At this time, only title/url/text are saved.

I also cleaned up some spots that were still using the modal for comments, which was broken (#716, #721).

I also found that replying to comments with no post context (e.g., inbox replies, user profile comments) is currently broken (to be addressed later).

P.S. I would like to do undo/redo in the future as well.

Issue Being Fixed

Inability to save drafts.

Screenshots / Recordings

qemu-system-x86_64_z2Z9WOrgGJ.mp4

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[CTalvio]

YYYYEEEEEEEESSSSSSSSS!!!!!!!!!

[hjiangsu]

First of all, thanks for taking this on! This is going to be a really nice QoL feature to have :D

I just left a few comments on some parts to consider, but other than those, I think it was done pretty well! One test I would also try out is import/exporting settings and see if the drafts also come with it. I think the appropriate behaviour there is to ensure that we ignore the drafts when we export/import settings