Also generate .gitignore files

[Tarrasch]

It would be good if we generated .gitignore files. It serves at least two purposes:

• It's convenient and nice. I don't need to make my working tree dirty by running the generator. 👍
• We give a clear best practice on the issue if we recommend users to actually commit the small files like testdata.yaml and grader.py. 👍 Currently I don't know if I should or shouldn't commit the files ...

[simonlindholm]

The problem is that different contests have different policies... some want secret/ committed, others (like PO) don't. Committing testdata.yaml is fine, I'd say.

[simonlindholm]

An option would be to add a generate_gitignore command, which you could remove if you want.