Add projection operation

[adamkarvonen]

I have been experimenting with the linear, piece-wise, and projection operations for representation control. It would be useful to have the projection operation available for reference to make sure my implementation matches what was used in the paper. But, it's currently not implemented.

representation-engineering/repe/rep_control_reading_vec.py

Lines 93 to 95 in 8de198b

	elif operator == 'projection':
	def op(current, controller):
	raise NotImplementedError

[andyzoujm]

I think something like
return current - (current * controller).sum(-1, keepdim=True) * controller / controller.norm(-1, keepdim=True)