What would you like to be added:

We should version the README.md KEP template file and ensure that PRs that update the README files under https://github.com/kubernetes/enhancements/tree/master/keps have been updated to use the latest template.

Why is this needed:

Occasionally there are updates to the KEP templates in between releases and when the templates change between enhancement stages it:

• Extra work on the enhancements team as they need to ensure that each enhancement opted into a release is using the latest template (which today is a manual process)
• Confusion and risk for enhancement authors who may not have been aware that the templates changed, and updates are required when updating the KEPs to be included in a release.

https://kubernetes.slack.com/archives/CPNHUMN74/p1675716127904979
This also happened between v1.24 and v1.25 when the Test Plan section of the KEP template was updated.

Proposal

• Add a version identified to the KEP template
• Add a PR job to https://github.com/kubernetes/enhancements to validate that and PR updating a README.md file under https://github.com/kubernetes/enhancements/tree/master/keps is using the latest version of the template
• Add a changelist file to track updates to the KEP template (so authors can easily see what has changed when they need to update their KEP

We could also consider adding logic to the PR job to ensure the ToC / basic structure of the README.md files containers required sections.