Miscellaneous updates to the registry

[johnmcollier]

There's a few miscellaneous updates that this PR groups together:

• Adds missing JBoss stack.
  • Looks like I missed this one when setting up the repo.
  • Comes from Add JBoss EAP XP 2.0 odo-devfiles/registry#67
• Adds missing description to the other JBoss stack
  • Comes from the meta.yaml in Add JBoss EAP XP 2.0 odo-devfiles/registry#67
• Updates to use a specific index server base image that doesn't have certain "Community Devfile Registry" fields set
  • Temporary workaround til Improvements and QOL fixes for the registry viewer devfile/api#605 is merged
• Adds basic contributing.MD (same as devfile/registry repo)