Automate PR review assignment with CODEOWNERS

[MarkEWaite]

Add CODEOWNERS to request reviews on code changes

GitHUb documentation describes how CODEOWNERS automates the assignment of pull request reviewers based on file naming patterns.

Created with OpenRewrite command:

$ mvn -U org.openrewrite.maven:rewrite-maven-plugin:run \
      -Drewrite.recipeArtifactCoordinates=org.openrewrite.recipe:rewrite-jenkins:RELEASE \
      -Drewrite.activeRecipes=org.openrewrite.jenkins.github.AddTeamToCodeowners

Testing done

Confirmed in other repositories that the CODEOWNERS file is a helpful addition. Rely on GitHub to check the validity of the CODEOWNERS file during the pull request review process.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue