Make sure the downloaded scrpt has execution permissions.

This change was apparently older than I thought...

Requires scdoc to generate a manpage.

See https://git.sr.ht/~sircmpwn/scdoc

Show that on when detecting the installation is already there.

No more running `virtualatex -h` and getting an error.

TinyTex is licensed GPL2, but this is GPL3. It can for practical
purposes be considered a derivative work.

IANAL, if this is a problem I can just re-license to GPL2.

- Add TODO
- Add version
- Comment scary `rm -rf` usage

This is the first beta version, it's already useful.

For some reason this doesn't work unless installed one by one...

One less dependency on external servers...