Feature proposal: generate CDEvents for Shipwright

[afrittoli]

CDEvents is a CDF project that provides a common specification for Continuous Delivery events.

Tekton natively supports generating CloudEvents, and thus Shipwright does through Tekton, however those events only describe low level abstractions like "TaskRun started" or "TaskRun finished".

CDEvents has a dedicated abstraction for builds which would be a good fit for Shipwright. My proposal is to let Shipwright generate CDEvents associated to builds. This could be achieved either by adding support in the Shipwright controller or through an external controller like that implemented in Tekton experimental.