make htmlSC available as GitHub Action

[gernotstarke]

for all those static-websites built with Jekyll, Hugo or the like -> a detailed check with HSC would really help.

We just migrated one of the arc42 sites from Netlify (back) to GitHub - and got numerous errors due to a lack of automated testing :-)

[ascheman]

Yes, great idea, thanks (had the same thought as I am using more and more GH actions lately.)
We could easily realize that based on the CLI (#318) implementation 😬 soon after releasing it (which is planned for next week).

[gernotstarke]

sounds awesome. Having a cli app would surely make hSC much more usable by non-Java people...