Documentation needed for the partitioning writer

[CTTY]

Is your feature request related to a problem or challenge?

We need to add more detailed documentation and examples to help people get onboard with the new partitioning writer.

https://github.com/apache/iceberg-rust/pull/1735/files#diff-5b069be1d9bc197f57228c775fcbfc6b30a440964d294b48ebb02318e3c7b936R252

Describe the solution you'd like

No response

Willingness to contribute

I can contribute to this feature independently