DOC: mention .attrs are preserved in Parquet IO for pyarrow engine
This PR adds documentation to `DataFrame.to_parquet` and `pandas.read_parquet` highlighting that `DataFrame.attrs` are preserved when using the "pyarrow" engine.

This behavior is already implemented in `pandas/io/parquet/pyarrow.py`, but was undocumented. This PR improves discoverability for users.

- [x] Added `Notes` section in both docstrings
- [ ] (Optional) Will add test in follow-up if needed

First-time contributor 😊

Thanks for the PR, but I don't think we need to necessarily document this so closing. Happy to have your contributions on other issues labeled `good first issue` >  I don't think we need to necessarily document this

Given that this is a behaviour that is rather unique to the parquet format (most other IO methods in pandas don't preserve attrs, I think?), and also something that differs between both engines, this seems worth mentioning in the docs? I’m fine with this if the author can get the CI green