main: status check for changes to versions and schemas folder

[ralfhandl]

This PR adds a workflow that checks for changes to files in the schemas and versions folder.

This workflow SHOULD NOT become a required check because

• we still need to add future spec versions to the versions folder
• we want to propagate new spec versions from main to dev and vX.Y-dev etc.

So this will be a "red flag" that can be disregarded, which is better than no warning, and may help to prevent accidents such as #4328 targeting the wrong file.

Tick one of the following options:

• schema changes are included in this pull request
• schema changes are needed for this pull request but not done yet
• no schema changes are needed for this pull request

[lornajane]

Mostly because I'm curious: why do it this way rather than with a path filter that would fire when we changed anything in the matching paths?

[ralfhandl]

Thanks, let's try that 😄

[ralfhandl]

Closed in favor of

• main: minimalistic check for changes to versions and schemas folder #4407