move CLI parsing out of controller, bump 0.5.12
Add CLI arguments to pick custom fonts

Users can now pick custom fonts via args `--textfont` and `--monofont`.
This is a WIP patch. Todos:
- Add more font candidates to the "default" font lists
- Add help text for arguments
- Perhaps a config file
show request time status, add request timeout
implement alt-shortcuts for buttons
fix bug when visiting relative url from root

enforce max header length too
correctly read response header

wrap words instead of char
bump version 0.5.8
don't check tls cert for now

Turns out there are more self-signed sites than otherwise. Apparently
the generally accepted way for gemini is trust-on-first-use. Before I
can implement that properly I'll just turn off cert validation
ctrl-l to jump to address bar
block user interactions during controller callback
more lenient address input
run curio in a separate thread

So that tkinter's mainloop() can take full control of the main thread
and we don't need to repeatedly run the heavy update() method anymore.
more info for pypi
safer arrow characters I guess
more responsive UI, full disclosure