Add a new workflow to ensure that new contributions are correctly typed

[moi90]

(This is a spin-off of #127.)

[trinamic-bp]

While we appreciate the idea of automated checks on pull requests, we are hesitant to rely on a relatively unknown GitHub Action.
The inline annotations produced by Reviewdog are a nice feature, but a simple green/red status output with detailed logs should be sufficient for our needs.

We will work on reducing the current issues flagged by static code analysis tools, and then introduce very plain and simple workflows to check pull requests.

[moi90]

Ok :)

[moi90]

I chose reviewdog, because it only critiques lines that were actually touched by a pull request. (Not primarily because of the inline annotations.) I didn't want to burden contributors with errors they didn't introduce themselves.