Post/comment drafts

[shilangyu]

Is your feature request related to a problem? Please describe.

See #255

Describe the solution you'd like

Drafts are automatically saved. When navigating back to a write post/comment screen which references the same target, the saved details should be autofilled. There should be no confirmation dialog when exiting.

• When a comment is left unfinished it is saved as a draft and can be restored later
• When a post is left unfinished it is saved as a draft and can be restored later

Things to consider

• Should there be a screen where one can explore all drafts?
• How could one discard a draft? It might be annoying that details are autofilled when someone just wants to write a new comment/post
• Should it be possible to have multiple drafts for the same target?
• Should there be drafts for messages as well?