Add announcement on Node 16 deprecation

[angelapwen]

Make the announcement in the issue visible via the Action changelog and the README.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Confirm the readme has been updated if necessary.
• Confirm the changelog has been updated if necessary.

[aeisenberg]

Looks good.

One more suggestion. Can we detect when this warning is emitted and emit a second warning pointing to the issue for more information (only if the original warning is also emitted)?

[angelapwen]

Thanks!

One more suggestion. Can we detect when this warning is emitted and emit a second warning pointing to the issue for more information (only if the original warning is also emitted)?

Hm.. that's an interesting idea. I'm not sure actually, I think it will be more clear once the warning is actually emitted. But so far I don't think we've used a mechanism to catch underlying Actions warnings.

[aeisenberg]

After the warning starts being emitted, it will be emitted for every workflow run? If so, we can wait until it's emitted and then include a custom warning that links to the issue.

[angelapwen]

After the warning starts being emitted, it will be emitted for every workflow run? If so, we can wait until it's emitted and then include a custom warning that links to the issue.

Yes, I think so — at least that's what I understood from the Changelog post: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/