docs: README.md Do not hardcode the supported versions of Python

Fixes: #2879 Fixes: #2881

Python 3.7 went end-of-life this week.

Also,

• ruff --ignore=E721
• Lint_Python takes ~5 seconds, so wait for it to pass before running the full matrix of tests.
• Remove outdated macOS_Catalina.md file.
• Replace deprecated npm config set python with environment variable npm_config_python.

Checklist

• npm install && npm test passes
• tests are included
• documentation is changed or added
• commit message follows commit guidelines

Description of change

README.md Do not hardcode the supported versions of Python