Heading markdown fix (#908)

* Copy heading parser and adjust it to match Reddit behavior

Unlike CommonMark, Reddit does not require space after #. This behavior is
coded in a private static function, so the only way to override it is to
copy everything and use the modified copy instead of the default parser.

* Use RedditHeadingPlugin instead of regexes

* Apply plugins to post body when writing a comment

This fixes display when writing comment to a post
that contains spoilers or headings without space

* Apply plugins to parent comment body when writing a comment

This fixes display when replying to a comment that contains strikethrough text

0 files changed, 0 insertions, 0 deletions