Document the release process for published operator images

[dwinchell]

No description provided.

[andykrohg]

Leaving some notes here until I have time to document this more formally:

1. Open a PR in this repository against the develop branch. Travis build should complete successfully along with peer review. Be sure to increment the VERSION field in hack/operate.conf appropriately.
2. Once merged, the build on develop pushes quay.io/redhatgov/tssc-operator:develop and quay.io/redhatgov/tssc-operator:VERSION-dev, where VERSION is represented by the version in hack/operate.conf.
3. Open a PR to promote develop into main.
4. Once this is merged, Travis will push quay.io/redhatgov/tssc-operator:latest and quay.io/redhatgov/tssc-operator:VERSION
5. Open a PR against the develop branch of https://github.com/RedHatGov/operator-catalog, incrementing the version of the tssc-operator image in operator-catalog.yml.
6. Once merged, Github Actions will push quay.io/redhatgov/operator-catalog:develop and quay.io/redhatgov/operator-catalog:VERSION-dev to quay, where VERSION is the version of the catalog itself specified in operator-catalog.yml. Either of these images can be used with your CatalogSource to test OLM integration for your newly-introduced changes.
7. Then promote develop to main in the operator-catalog repo. Once this is merged, quay.io/redhatgov/operator-catalog:latest and quay.io/redhatgov/operator-catalog:VERSION are pushed to quay