Master issue for documentation and examples

libui is not yet well-documented. I started fixing this with utflib-and-attrstr, but we still have a while to go.

I have yet to find a documentation system I'm happy with. I am intending on writing my own, but am not sure when (if) that will happen again (since my first attempt didn't go smoothly; and even then I would need copyright clearance to continue working on it).

Ideally the documentation system should be similar to godoc with the addition of Markdown-formatted articles alongside the documentation and as Overview sections on each page.

The Go package ui already has somewhat better documentation I should try to integrate with libui somehow. A way to automatically propagate documentation to package ui would be a pipe dream.

The Go code is devoid of examples, and the API changes means old examples people still turn to don't work.

I'm not sure what problems people have with the documentation and examples that *are* there on both repositories, but that's also worth addressing.

I also need to figure out what to do about the wikis on GitHub.