Feature request

As part of preparing the experimental new filters API to Beta (tracked here: knative/eventing#5204), we should add support to kn to create these filters when creating a trigger.

Use case

With the new filters API entering Beta, more users will want to try it out. It would be convenient for them if they can use kn to create them, instead of being required to use yaml files to try out the new filters.

UI Example

kn trigger create mytrigger --new-filter filtertype=filtervalue