community/erlang-observer: broken out of the box

I recently tried to get erlang-observer package to work on clean Alpine 3.15.0 install (because edge has the same package) and found a few issues to get it to work.

All detailed in a blog post but in a nutshell:

1. missing erlang-wx dependency (without which it doesn't start)
2. missing xauth dependency (without which X11 can't be forwarded)
3. missing terminus-font dependency (without which it looks like this)
4. x11 forwarding disabled in sshd

The first two I'm reasonably confident should be fixed in the package.

The third one I'm not sure -- it could be quirk of my setup, it could be generic. But since it's a single package dependency and clocking at 2.71 MB, I'd probably err on the side of caution.

The fourth one is probably not worth fixing; I'm just mentioning it for completeness sake.

I'll try and come up with a MR for the first three issues shortly.