feat: add ability to toggle operator filter on and off

[RobPando]

This should be highly considered and suggested by OpenSea publicly. Assuming OpenSea is 100% looking out for creators, giving them the ability to opt out of this solution completely by ignoring it entirely if the owners decide to, is the best way forward. Expecting the creators to add immutable code to their forever contracts on the blockchain is not looking out for creators in its entirety. This seems like a decent compromise and A step forward towards an optimal solution.

[operatorfilterer]

Since the registry allows contracts to unregister themselves to bypass checks once externally called, a permanent revocation is probably more useful - see #29