Add ability to specify option to generate hashes within pyproject.toml

[asmith26]

Please note: I haven't written any Rust before, but just wanted this feature hence thought I'd try submitting a PR for this. I've essentially tried to mimic the code regarding the --with-sources feature. I'm not sure how to compile and test locally (so welcome any info on this - and if helpful I would be happy to test this locally and get back to confirm if this works).

All thoughts/help/feedback etc. very welcome, and no worries if this feature is not useful.

• Adds ability to specify option to generate hashes via the pyproject.toml (similar to https://rye.astral.sh/guide/pyproject/#toolryelock-with-sources).
• Updates doc regarding the --generate-hashes option too.
• Added +++ 0.35.0 to the doc in case it gets merged for this version, but feel free to amend as appropriate.

Thanks!