Subshell 0.77.0-beta.7

Seventh public beta of Subshell.

Highlights:

• Comment author avatars in threads, with a setting to turn them off.
• An open drawer closes on Back or a scrim tap even with comment swipe actions on.
• Moderators can send a removal message after removing a post or comment, with saved responses that can be backed up.
• One composer family everywhere: the same editor, formatting bar, preview and buttons in posts, comments, chat, modmail and New message.
• Editing a post or comment asks before discarding unsaved changes.