Implement validation of list types

[JakobGM]

The following model should be able to validate columns containing lists of strings for instance:

import patito as pt

class MyModel(pt.Model):
	my_column: list[str]

Used in this context:

df = pl.DataFrame({"my_column": [[1], [1,2], [1, 2, 3]]})
MyModel.validate(df)