Markdown preview
Adds server-side previews for Markdown (#25 (closed)).
This is fully functional but still needs some visual design. For example, I think the "Edit"/"Preview" buttons would look good in line with the form caption "Text (Markdown)", but between all of the flex boxes the layout is somewhat fragile. Also, I couldn't get the Spectre loading worm to inline properly into a button group.
It might make more sense to have tabs instead of a button group.
Having ic-target
refer to a specific element where js-markdown-*-button
navigate the DOM manually is a bit ugly, but ultimately results in less spaghetti.