As expected, implementing that "follow" mode for [lariza] is rather
frustrating. It's pretty slow, probably a WebKit issue, because [Vimium]
does even more stuff. There appears to be no way around calling
`getBoundingClientRect()` -- that causes the slowdowns.

Why `getBoundingClientRect()`? To find an appropriate place to put the
labels. Okay, well, the sad thing is, this often doesn't work, either.
So ... I might resort to something even more trivial after all. The
other "follow" scripts for surf do this, too.

Vimium works reasonably well, but it's also pretty complicated. And it's
written in CoffeeScript, which is terrible to read, so I don't have a
lot of motivation to find out exactly what Vimium is doing.

Yeah. Might go for a really simple implementation. That will work on
simple / sensible web sites. For all the other ones, use the damn mouse.

[lariza]: https://uninformativ.de/git/lariza
[Vimium]: https://github.com/philc/vimium