DO NOT SUBMIT: Generate v1.4.2 release artifacts

[wantehchang]

Steps to verify that the binary artifacts are correctly generated:

• Create a draft Pull Request such as this one (change the trigger from release to pull_request and use actions/upload-artifact instead of actions/upload-release-asset),
• Wait for all Continuous Integration tests to pass,
• For each "CI Linux/macOS/Windows Release Artifacts" workflow:
  • Click on it,
  • Expand the "Upload artifacts" section,
  • Download the archive from the link given after "Artifact download URL",
  • Unzip it twice,
  • Test the binaries with avifenc --version and/or by (de)compressing images.
• Close the Pull Request without merging it.