introduce CI job to run codespell

[abbbi]

I dont know what the policy is, just a little codespell CI workflow (for all branches, though) on files where it makes sense to have some simple spelling checks in place :-)

Running codespell is part of the Debian QA process and common QA tools such as lintian will complain if manpages etc contain typos/spelling issues, so instead of opening a pull request each time i encounter one it may make sense to run this proactively.

[bagder]

It found a typo...

[abbbi]

It found a typo...

awesome, it works :)

[bagder]

Thanks!