Update and drop unsupported dependencies

[offbyone]

I had a look at the code and I'm not sure what requirements you'd want for dropping older Python versions, but I'd be happy to make a PR that drops a bunch of the old versions, probably including some apparently-dead filters. I use this in my Pelican blog, and I'm looking to have to freeze the Python version I use at 3.12, or find some other way to bundle up my javascript and CSS and run sass, none of which I want to do :)

A few issues that might be resolved by this:

• Threading.isAlive was removed in Python 3.9  #528
• Deprecation warning due to invalid escape sequences in Python 3.7 #531
• yuicompressor is a security placeholder on pypi: https://pypi.org/project/yuicompressor/

Would you be up for a modernization and refresh of the code? I'd be looking at:

• switch to pyproject.toml to define the project
• use uv and locking for dependencies
• drop all Python versions older than 3.10
• add github actions CI

[samuelhwilliams]

This would be great 👀 Would love to see this get in, but definitely feel a mild feeling that this is a dead repo now?