Update Test Workflow

[ntno]

Description

Fixes the Test PR GitHub Action workflow which is currently broken.

• minimum tested Python version is now 3.8 (up from 3.7)
• maximum tested Python version is now 3.12 (up from 3.10)
• upgraded checkout action step
• upgraded python action step
• fixed tidy-html5 library install on mac-os runner (required for testing)

References

install instructions for tidy-html5: https://github.com/htacg/tidy-html5/blob/next/README/BUILD.md

Testing

• workflows are passing
• no code changes other than version bump

Checklist

• I have added documentation for new/changed functionality in this PR or in mkdocs-terminal/documentation
• All active GitHub checks for tests, formatting, and security are passing