Plugin Release v3.4.0-gradle

[github-actions]

Requirements

• ⚠️ Ensure the release process has succeeded before proceeding

GCS

• Run ./jib-gradle-plugin/scripts/update_gcs_latest.sh 3.4.0 script to update GCS with the latest version number

Github

• Update CHANGELOG.md
• Update README.md
• Search/replace the old published version with the new published version in examples
• Publish Release
• Merge PR (gradle release v3.4.0 #4109)

Jib-Extensions

• Update versions in Jib Extensions
• If there were Gradle API or Jib API changes, double-check compatibility and update Version Matrix on jib-extensions. It may require re-releasing first-party extensions. See jib-extensions#45, jib-extensions#44, and jib-extensions#42