Add automation to flag PRs on areas without an active SIG/project

[joaopgrassi]

Fixes ##2834

Changes

This PR adds automation to flag and auto-close PRs with changes on semantic convention areas that do not have an active sig/project. It does so by:

• Getting all the changed files inside the model/ folder the PR is proposing
• Then check if there is an active sig/project for the modified areas
• If not, the PR is closed with the label triage:rejected:declined
• Maintainers/Approvers can bypass the check by adding the label triage:accepted:ready (if the PR gets closed, apply the label first and then re-opening the PR)

I decided to go with Javascript for the scripts as that seems to be the common pattern for it. I initially wanted to use github-script for the action, but decided against it because it just added complexity where not needed. Also, the way it is now I can use "some" Typescript features to easy the development part. Node 22+ has type stripping so at least we get some IDE help. Much better than bash scripts :D

This is how the comment will look like:

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• Links to the prototypes or existing instrumentations (when adding or changing conventions)