Epic: Add a Release Process

[bobcatfish]

Expected Behavior

• We should have versioned releases (https://github.com/knative/build-pipeline/releases)
• We should publish all images as part of a release (including the entrypoint image and any other images we depend on)
• We should publish yaml that can be used to deploy the Pipeline

Actual Behavior

• Currently the only way to setup the Pipeline is to run ko as described in the DEVELOPMENT guide
• There is no versioning or release process of any kind

[bobcatfish]

We currently have nightly releases, so I'm going to close this in favor of #383