Add example for how to read/write encrypted parquet files

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

• Part of [Epic] Parquet Modular Encryption Support #7278

Thanks to @rok @adamreeve and others the parquet crate now has the ability to read encrypted files (#6637)

We should document this with some examples to help users understand how it can be used

Describe the solution you'd like
Add an example of how to write

Describe alternatives you've considered

Perhaps we can add an example here below the basic ones:

• https://docs.rs/parquet/latest/parquet/arrow/index.html

Additional context

[alamb]

label_issue.py automatically added labels {'parquet'} from #6637

[alamb]

label_issue.py automatically added labels {'documentation'} from #7283