[docs] Process Parquet files
This PR adds a guide for how to process Parquet files:

- Eager dataframes with `pd/pl.read_parquet`
- Lazy dataframes with `pl.scan_parquet`
- Read and query with DuckDB
[docs] Process Parquet files: This PR adds a guide for how to process Parquet files:

- Eager dataframes with `pd/pl.read_parquet`
- Lazy dataframes with `pl.scan_parquet`
- Read and query with DuckDB