All your hints are belong to us

In https://github.com/googlefonts/fontmake-rs/issues/33#issuecomment-1346920324 concerns about hints came up. It then became unclear what the existing fontmake tooling actually supports. Based on #33 and IM conversation I current believe that:

* Glyphs can embed hinting information but fontmake wouldn't read or compile it
* Tools exist to stick hints directly into the binary (or ttx), any outline edit would presumably invalidate the hints
* @davelab6 noted "the hint byte code is turned into assembly in .TTX files, and can be read in a text editor; and fontforge provides a step debugger for TT assembly via FreeType."
* People aspire to stick hint information into UFOs but fontmake does not read or compile it
* See https://unifiedfontobject.org/versions/ufo3/lib.plist/#publictruetypeinstructions, https://unifiedfontobject.org/versions/ufo3/glyphs/glif/#publictruetypeinstructions.
* https://github.com/googlefonts/ufo2ft/pull/654 aims to add fontmake support for ^

(will update as I learn more)