Add a Python script to run Molecule tests

[tanhaow]

So we can also test it locally instead of always needing to push to run it on GitHub CI.

[rlskoeser]

Here's the script in princeton ansible https://github.com/pulibrary/princeton_ansible/blob/main/run_molecule.py

It includes logic to run changed roles or their dependencies (probably useful); we need to make sure it runs molecule test with --all since we'll have at least one test with scenarios after #287 is merged.