Update gitignore, flake8, and pre-commit config files

[willingc]

Addresses #78.

This PR updates and documents the following configuration files:

• .gitignore (use standard Python gitignore and move pyosMeta specific items to end)
• .flake8 (explain ignored rules and add a code complexity check)
• .precommit.config.yaml (improve comments for maintainability and new contributor friendliness)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.64%. Comparing base (b3fae4e) to head (4f0570c).
Report is 10 commits behind head on main.

❗ Current head 4f0570c differs from pull request most recent head 16d2013. Consider uploading reports for the commit 16d2013 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #101   +/-   ##
=======================================
  Coverage   41.64%   41.64%           
=======================================
  Files           4        4           
  Lines         461      461           
  Branches       74       74           
=======================================
  Hits          192      192           
  Misses        268      268           
  Partials        1        1           

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[lwasser]

@willingc thank you for this. see what you think about removing some of the things we don't need or let me know if you think we should keep the default as is. once we clean this up we can merge this. approving!

[lwasser]

Thank you this is wonderful!