[Feature]: Predator functional response

[Rick-Methot-NOAA]

Describe the solution you would like.

The current code assumes that M2 increases linearly with predator abundance. But it really should depend on abundance of both predators and prey. From Wikipedia on predator functional response: https://en.wikipedia.org/wiki/Functional_response

Describe alternatives you have considered

wait for FIMS

Statistical validity, if applicable

No response

Describe if this is needed for a management application

No response

Additional context

No response