This commit implements rendering comments from the `["comment",
<COMMENT_TEXT>]` tag in a highlight note.
Comment contents get rendered like a kind 1 note's "content" field
This commit also adds the `r` "reference" tag as a standard tag reference type
Changelog-Added: Add support for rendering highlights with comments
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
d71d448ac8