DO NOT SUBMIT: Generate v1.4.0 release artifacts

[wantehchang]

No description provided.

[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.

[wantehchang]

I tested avifenc, avifdec, and avifgainmaputil binaries in the CI Linux and macOS Release Artifacts. I will test on my Windows laptop when I get home.

[wantehchang]

I tested avifenc, avifdec, and avifgainmaputil binaries in the CI Windows Release Artifacts.

[y-guyon]

https://github.com/AOMediaCodec/libavif/releases/tag/v1.3.0 already has binary artifacts. Is this for v1.4.0?

[wantehchang]

Yannis: Yes, this is the test PR for v1.4.0. I put v1.3.0 in the title of the PR because this PR cannot change the version number. Sorry about the confusion. I just changed the title to say v1.4.0.