Build tools for generating registry based on registry/catalog info on a github repo

[elsony]

User Story

As a devfile admin, I want to generate a devfile registry based on the content in a registry catalog repo that defines all the available stacks to be added to the registry.

Acceptance Criteria

• It should read the content of a given registry catalog repo to gather all the info on the list of stacks to be include in the registry
• It should build a devfile registry packaged in the form as described in Initial design on packaging of devfile registry for deployment #163

Links

• Related issue:
  Initial design on packaging of devfile registry for deployment #163
  This item is part of the epic OCI-based registry support #82

[johnmcollier]

I've put a PR up (devfile/registry#1) for review that implements the following:

1. Build scripts and docker file for producing a Devfile index docker container, as outlined in Initial design on packaging of devfile registry for deployment #163
2. GitHub workflow actions for running the build on PRs and publishing new images to Quay.io