Minor update to documentation

[D3SL]

For "other tools": Polars, Python's equivalent to data.table but with more tidy-like syntax, directly supports parquet including "lazy" operations.

For limitations: This may be parquet in general but loading a parquet file in Arrow keeps it locked somehow. Attempting to write to that same file from python while the dataframe exists in R causes problems. Sometimes the lock is so bad I need to rm() the file in R, force a garbage collect, and then delete the parquet file to get new data loading into R again.

If nanoparquet doesn't have this limitation that would be a very significant improvement in QOL, if it does it's worth mentioning.