Fix some minor typos, bugs and the GitHub CI workflows

[nmnobre]

Hi @Yixin-Hu, @danielepanozzo,

These are just some quality-of-life improvements/updates to keep the project alive. :-) It'd be nice if we could have a chat (even if just via email) about some new features I'm implementing.

Kind regards, -Nuno Nobre

[MariusCausemann]

Hi @nmnobre , I have an issue with a segfault in the preprocessing phase ( issue #75 ). Since you fixed an issue with a data race in this stage, I was wondering if my problem and the issue you spotted could be related?