Add tkn verify/validate subcommand #2588
Description
Feature request
Add a new subcommand to the tkn cli to verify/validate pipeline syntax. There is a dru-run flag, but it requires k8s cluster or at least credentials. Instead we can de-serialize the yaml file and try to create the Tekton resource, which does not require k8s clusters or credentials.
Furthermore we can also test for remote resolutions of referenced objects.