macOS CEF host package

[jwosty]

This is tricky because at the moment there don't seem to be any bindings to CEF that work on macOS. CEFSharp, which is what we use for Windows, definitely can't work because it uses CLI C++. In theory there's no reason why it shouldn't be possible.

[jwosty]

Possible routes to resolution:

• get CefGlue working on macOS (lots of unknowns here)
• generate my own .Net wrappers for Chromium that works on macOS (sounds like a lot of work to maintain)
• implement the Interstellar API in C and then wrap it in P/Invokes (gross but it would work)