Allow filtering out normal events

[mmckeen]

Description

Normal events can often be noisy, and for many use cases all we care about is Warning events.

That said, add the ability to only report non-normal events via a flag.

Testing

Tested using a kube cluster, works as expected.

[mmckeen]

@max-rocket-internet let me file an issue for test coverage, I also have a few other feature-requests/ideas I'll file into the backlog 🙇