feat(geometry): add support for css three value format

[NSPC911]

This shouldn't change much of other people's code, it just adds support for padding with 3 values

According to the mdn web docs, a triple value should be read such that the first value is the top, second is the sides and third is the bottom. This adds support for it. Yes, this has been tested in an app, but I'm not sure what modification I need to make to the tests/test_geometry.py file.

Please review the following checklist.

• [x] Docstrings on all new or modified functions / classes
• [ ] Updated documentation
• [ ] Updated CHANGELOG.md (where appropriate)