Implement __getattr__ for Prior class

[wd60622]

I would be nice to be able to dot into Prior class and get the parameter. For instance dist.mu. Would be similar or same implementation to this:

pymc-marketing/pymc_marketing/prior.py

Lines 396 to 398 in 9684821

	def __getitem__(self, key: str) -> Prior | Any:
	"""Return the parameter of the prior."""
	return self.parameters[key]