Allow observation of WebHook Events

[ebullient]

trafficstars

The usecase: GitHub Sponsor events are pure WebHook events. They are not associated with or assigned to a GitHub App Installation.

It should be possible for my bot to handle those requests (too), but at the moment, the Quarkus GitHub App makes assumptions about the presence of an installation id.

This is a start for allowing plain webhook events to overlay handling (i.e. can also be routed or replayed w/ smee).

What I have is a (bad) start at managing these events.