Scheduled CI for Iron (backport #401)

[mergify]

Similar to #398

---

This is an automatic backport of pull request #401 done by Mergify.

[mergify]

Cherry-pick of 38504d1 has failed:

On branch mergify/bp/iron/pr-401
Your branch is up to date with 'origin/iron'.

You are currently cherry-picking commit 38504d1.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   README.md

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both added:      .github/workflows/ci-iron.yaml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally