[DOC] Add a Benchmarks, FAQ, and Known Issues Section to cudf.polars docs

[Matt711]

Report incorrect documentation

Location of documentation to be improved
https://docs.rapids.ai/api/cudf/stable/cudf_polars/

Describe the problems or issues found in the documentation
We can follow cudf.pandas https://docs.rapids.ai/api/cudf/stable/cudf_pandas/. We should sections for benchmarks, frequently asked questions, and known issues.

Suggested fix for documentation
Concretely, I suggest we add these sections to https://docs.rapids.ai/api/cudf/stable/cudf_polars/

• Usage
• Benchmarks
• How it Works
• FAQ and Known Issues