add ability to create webhook that filter by object type

[raffaelespazzoli]

this would allow to minimize the calls to the webhook.
see also here: https://kubernetes.io/docs/reference/access-authn-authz/extensible-admission-controllers/#matching-requests-objectselector

[raffaelespazzoli]

For mutation, the needed objects can be calculated on the fly based on the currently defined Assign, AssignMeta.
Not sure if this is possible for valudations.

[romerobu]

HI @raffaelespazzoli have you made any progress on that?