alkment

### Description DataFrame.tail and DataFrame.head support negative integers for the n argument. It would be great if the GroupBy.tail and head methods supported the same behavior. Passing a negative value...

The current version (0.14.12) of polars-xdt seems to be incompatible with polars==0.20.23 The following snippet can be used to replicate the error. ` pl.DataFrame({'d':[datetime.date.today(),datetime.date.today()]}).with_columns(pl.col('d').xdt.offset_by('1bd'))` This raises a `PanicException: not implemented`...