Better studyset editing layout, formatting (bold/subscript/superscript/etc), and mobile-friendly layout

[ehanahamed]

Description
Right now, the studyset terms editing thingy is really basic and doesn't have text formatting options like bold, italic, underline, superscripts, subscripts, math formatting, etc that are really important for things like math or chemistry. (Dr. Illif reference)

The terms editor should have the term above the definition, vertically, on mobile so that it fits on their screen. Right now the editor just overflows horizontal and users have to scroll sideways. This currently not actually that bad, but it could be improved.

The editor should also have a little bar with Bold, Italic, Underline, Superscripts, Subscripts, Special Symbols, and other formatting options. I think it will show only a few of those options by default, and there will be a "more" or "show all" button that will expand the whole textbox to fill more screen space (on desktop)

Related
#28 - Bugs with the current studyset terms editor will be fixed after (or while) things are being rewritten for this change