Remove trailing whitespace, add pre-commit and CI workflow to check whitespace

[smkent]

This model is so useful! I've been printing a lot of Gridfinity bins and am starting to customize my own. That's led me to dig through the OpenSCAD code to make customizations.

To make development easier, this PR:

• Adds whitespace fixes -- removes trailing whitespace and adds newlines at the end of all files
• Adds pre-commit to fix these issues at commit time
  • A developer can enable these hooks with pre-commit install within their cloned repository
• Adds a GitHub Actions workflow to run pre-commit's whitespace checks on PRs, so all new code will be consistent

[smkent]

See this test PR in my fork and workflow run for an example of the GitHub Action being added.

[smkent]

Hi, is there interest in merging this PR? Thanks!

[Ruudjhuu]

Is there a way to show more information for the CI run? like line numbers?

[smkent]

Is there a way to show more information for the CI run? like line numbers?

Yep! Updated. Check it out: https://github.com/kennetek/gridfinity-rebuilt-openscad/actions/runs/7432741288/job/20224893804?pr=128

[smkent]

🎉