Add more lint checks to GHA

[willgearty]

There are a few lint checks that we should probably add to our github actions as soon as possible:

• E11x: other indentation issues (expected indented block, unexpected indent, not a multiple of four)
• F401: module imported but unused
• F811: redefinition of unused name
• F841: unused name

For reference, the various lint checks that are available are listed here: https://flake8.pycqa.org/en/latest/user/error-codes.html and https://pycodestyle.readthedocs.io/en/latest/intro.html#error-codes