Fix various documentation issues

I've synchronized the 'targets' with the list from README.md and alphabetically sorted them.
I've also fixed the issue/bug tracker link to point to here (salsa).
Lastly, I fixed Example 2 as the manpage tells to use python3 -m freedom-maker, while it should be just freedom-maker.

https://tracker.debian.org/pkg/freedom-maker mentions " 23 new commits since last upload, is it time to release?".
While I'm pretty sure a new 'upstream release' is out of the question in this stage of the freeze, the last 2 items probably would be allowed. I dunno how that should be organized (in this repo) though.

Feel free to squash the commits.