Add a test (or a github action) to catch static files issues early

[bmispelon]

I recently had to revert a commit because deploying it on the production server failed when running collectstatic, even though all the tests and github actions passed.

The issue is that the production server uses ManifestStaticFilesStorage for its static files, which adds a post-processing step the the collectstatic command and that step will crash with a ValueError if a missing static file is referenced (in my case, a minified javascript file had a comment referencing a .map file that had been deleted).

This type of issue should be caught early so we can fix it during the PR and avoid a revert.

[ontowhee]

I'm able to reproduce this locally by deleting jquery.min.map from the project and the static root folder, and then running python manage.py collectstatic --settings djangoproject.settings.prod and gives the error described in this issue.

I was trying to reproduce the error in #1837 and was expecting the tests to fail, but it is currently passing. There must be something I'm missing. Is it not picking up the production settings file? Is DEBUG variable true? I'll need to revisit this.