add slotscheck to CI

[ariebovenberg]

Summary

@zsol requested I add slotscheck to the CI.

Slotscheck prevents mistakes in __slots__ from creeping in again. Fixing slots in #605 resulted in big memory savings.

Instructions for pre-commit are documented here.

Test Plan

I've added slotscheck to the github build action. Let me know if you'd like it mentioned in CONTRIBUTING.md or README.rst

fixes #574

[ariebovenberg]

Hmm, I see slotscheck would need to add py36 support. It's EOL but I'm assuming you won't be dropping 3.6 anytime soon?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.78%. Comparing base (9563b4a) to head (ef4d363).
Report is 316 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #615   +/-   ##
=======================================
  Coverage   94.78%   94.78%           
=======================================
  Files         245      245           
  Lines       25238    25238           
=======================================
  Hits        23921    23921           
  Misses       1317     1317           

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[zsol]

Thank you!

Yes, please add a note in README.rst about running slotscheck.

[ariebovenberg]

An interesting failure -- investigating 👀