rich text support

This MR adds support for formatting posts in something other than Twitter-style plain text. HTML and Markdown modes are supplied, abstraction is provided to also enable BBCode parsing, but we will need to roll our own parser for that.

enabled an automatic merge when the pipeline for e7871ed0 succeeds

merged

mentioned in commit a26d5e6b

mentioned in merge request pleroma-fe!325 (merged)

mentioned in issue #275 (closed)

Nice, but please wait for a round of review before merging this kind of non-obvious features next time :)

mentioned in commit 58539e13

mentioned in merge request !313 (merged)

mentioned in merge request pleroma-fe!331 (merged)

mentioned in merge request Toromino/pleroma!1 (merged)