(SQUASH PLS) Require exactly 1 change type label on every schema PR

[vcschapp]

Category

What kind of change is this?

Please select one of the following four options.

Consult Pull request merging criteria for a description of each category.

1. Cosmetic change.
2. Documentation change by member.
3. Documentation change by Overture tech writer.
4. Material change.

Description

Brief description of the business purpose and effect of the pull request.

This PR creates an automatic GitHub actions workflow that forces every pull request to have EXACTLY one (no more, no less) of the following change type labels:

The purpose behind this change is to:

1. Strengthen the mechanisms that will help us detect MAJOR schema changes and prevent their premature release. (See Schema versioning and stability on the Overture Confluence wiki).
2. Automatically enforce that every change is categorized.
3. Enable streamlining the PR template by allowing us to delete the change category section.

Reference

List of relevant links to GitHub issues, PRs, and other documentation.

1. Schema versioning and stability
2. Pull request merging criteria.
3. (SQUASH PLS) Include MAJOR change details in PR template #306

Testing

Brief description of the testing done for this change showing why you are confident it works as expected and does not introduce regressions. Provide sample output data where appropriate.

🦿 This is a self-bootstrapping change! It's making GitHub run the action on itself. So meta. So auto. So process! 🦾

Checklist

Checklist of tasks commonly-associated with schema pull requests. Please review the relevant checklists and ensure you do all the tasks that are required for the change you made.

1. Add relevant examples.
2. Add relevant counterexamples.
3. Update any counterexamples that became obsolete. For example, if a counterexample uses property A but is not intended to test property A's validity, and you made a schema change that invalidates property A in that counterexample, fix the counterexample to align it with your schema change.
4. Update in-schema documentation using plain English written in complete sentences, if an update is required.
5. Update Docusaurus documentation, if an update is required.
6. Review change with Overture technical writer to ensure any advanced documentation needs will be taken care of, unless the change is trivial and would not affect the documentation.

Documentation Website

Update the hyperlink below to put the pull request number in.

Docs preview for this PR.

[jenningsanderson]

❤️

[jwass]

Wow - I don't much about the github api for this but I assume it works and looks good to me.