Revisions to the devfile registry doc pages

[michael-valdron]

Which area this feature is related to?

/area documentation

Which area is this documentation change is related to?

/area registry

Issue details

What mistake did you find / what is missing in the documentation?

There is a few revisions that need to be made the devfile registry doc pages to ensure the content on these pages are up to date.

These revisions include:

• building-a-custom-devfile-registry.md
  • golang version updated
  • Dockerfile instruction updated
  • air gap environment manual added as additional resource
• creating-a-devfile-stack.md
  • Procedure steps 2 expanded
• deploying-a-devfile-registry.md
  • Deploying the devfile registry on Kubernetes cluster formatting fixed
• installation-of-in-cluster-offline-devfile-registry.md
  • Modify devfile verification step heading fixed
• adding-a-registry-schema.md
  • example headers fixed

Target Date: 04-03-2023

[michael-valdron]

Rebased task from devtools week 09/22, need to revise golang version as part of review feedback.

[michael-valdron]

Added as part of #1080 epic as these revisions work to providing updated information to new adopters of the devfile registry.

[michael-valdron]

Due to recent changes in our build process devfile/registry#174, the building a custom devfile registry guide has been revised.

[michael-valdron]

devfile/devfile-web#36 is ready for another review.