Create a starter workflow

[adangel]

See https://github.com/actions/starter-workflows

There is also an old PR (actions/starter-workflows#1200) which should be replaced by using this action now.

[adangel]

It turns out, the original PR (actions/starter-workflows#1200) has been updated (thanks @abirismyname !) and also merged.

To use in your projects, go to "Settings / Security & analysis" and set up "Code scanning". There you can choose now PMD:

I've created another PR to update to the latest v1.1.0 -> actions/starter-workflows#1324

Seems like this needs to be updated for every release as well (see also #3), as GitHub states: "We require that these actions be referenced using the full 40 character hash of the action's commit instead of a tag".