Fix invalid syntax of github action file

[errnesto]

Okay I'm very sorry for my messy contributions :-( The github action is still broken. I'm trying to clean it up here.

The last time. I tested the action locally with https://github.com/nektos/act where it worked fine, but the syntax for the action was still invalid.

By now I don't know if there is a good way to do this with only an action file. So I created a entrypoint.sh file and another Dockerfile. There it is easier to access the input variables from github.

And I added a "test" here: https://github.com/wunderundfitzig/linkcheck-action/runs/4301401999?check_suite_focus=true

[andrenarchy]

It would be great to see this merged and in a new release as soon as possible because the action is not usable for us currently.

[errnesto]

@filiph ping :-) I’m also happy to apply some changes to this. e.g. if you would prefer to use just one Dockerfile. Then the entrypoint.sh would just go unused in the normal case.

[filiph]

Thanks for the ping! To be honest, I don't know enough about Docker to review this. I hoped I'd have time by now to learn more, but I don't. I'll just merge it. Please let me know if there's anything else I need to do.

[tooomm]

@filiph Since your published action is sadly still not working in the GitHub Marketplace... do you mind trying to publish a new release targeting master? All changes in recent months (like this one) that were targeted at fixing the GH Action are not yet in a published release. It looks like you published the current version in February 2022, but targeted 2.0.20 from October 2021 (https://github.com/filiph/linkcheck/commit/69913d9df3600d9a165ab35380dfbe625f2ba617). Therefore the change in this PR is not included and distributed yet.

I created #95 and drafted a new release.