This App needs CI

[john-science]

I think we need a very basic CI to run this app (on its settings file), like once a month. Just to see if recent ARMI changes have broken it.

And maybe we run the same integration test every time somebody pushes to main.

Some notes on running a GitHub Actions CI on a schedule:

• Groovy scheduling syntax
• Crontab syntax for running once per month: 0 2 1 * *

[john-science]

As a quick starting point, I have added a GitHub Action to this repo that tests black formatting,