Add Tekton API docs (oc explain)

Problem:

Tekton API docs are not available and user has to look into Go code to get accurate description of the fields available on CRDs

Goal:

As a Tekton user, I want to have access to the Tekton API documentation through "oc explain" and also API explore in the Admin Console, so that I can easily find out available fields when creating Tekton resources and their documentations.

Why is it important?

To simplify creating Tekton resources

Acceptance criteria:

1. oc explain displays Tekton resources description and fields
2. Tekton resources description and fields are available in the Explore view in Admin Console