Add GitHub action workflow validation

[danielbachhuber]

We tried and failed previously: #81

It would be nice to get this working again.

I think we should create a new workflow file to temporarily test from, so we don't fail builds across all repos.

[jrfnl]

Might be a nice first step to add a yamllint workflow ? That should at least prevent typos and such from being merged in. (sorry, my bad, I made one earlier)

[tfrommen]

@danielbachhuber I added a new job using actionlint in #111. I know that you (specifically, @swissspidy) tried to use action-validator before, so can you maybe take a look if that would work for you instead?

[swissspidy]

Ah yes, I forgot about that. We added it in #79 but it didn't really work, there were some installation issues on CI that we couldn't figure out. Reverted in #83.

I don't know the difference between the two tools, but at first glance actionlint seems to be way more popular and battle-tested, so chances are higher that it works for us.

So #111 looks promising. I'll re-review ASAP.