Exploratory: Try porting to web-view

[AndrewRadev]

Right now, quickmd doesn't work on MacOS, because there's no working webview2gtk. It might work on windows, but it'd need GTK installed.

It might be nice to use the web-view project instead, since it seems like it's cross-platform and it uses whatever works on each platform... but it might be much more inconvenient to work with, with a lot of the logic needing to be in javascript. I have no realistic idea of how it would work.

HTML generation, file-watching, and configuration have nothing to do with GTK, so a good chunk of the logic might be fine without it. Whether web-view is convenient enough UI-wise is the big question.

It's something I'd try at some point, at least. Though maybe not even in this project, but in a separate one by copy-pasting stuff ¯\_(ツ)_/¯