release 1.6.0?

[eitsupi]

The next Python Polars update will introduce a lot of breaking changes on the Rust side that may take some time to catch up, so I wanted to release 1.6.0 before then (this weekend).

@etiennebacher Thoughts?

[etiennebacher]

tidypolars works fine with the current development version, so no problem to release 1.6.0.

Do you want to include #1635 in 1.6.0? I probably won't have time to review before tomorrow or Saturday.