Add check changeset workflow

[khiga8]

This PR introduces a workflow to ensure that every PR has a changeset and/or the skip changeset label.

Context: I forgot to add a changeset in a PR earlier, and scrambled to add it in a follow-up. Having this check in place will be helpful since it's easy to forget.

I copied the check changeset workflow over from Primer React!

[changeset-bot]

⚠️ No Changeset found

Latest commit: d2ab13c

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR