Added step for notification for pr creation

[vpaiu]

Description of changes:

• Added job for sending notification in case the PR is created.

Testing:

• Tested the metric publishing my fork: https://github.com/vpaiu/code-editor/actions/runs/17491197586
  By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[aderende]

nit: create-pr step should fail if pr were never created successfully. If pr were created create-pr step will succeed.
This eliminates the need for PR_CREATED variable, because it's only used to indicate that create-pr finished successfully. There is a built-in mechanism we can use: https://docs.github.com/en/actions/reference/workflows-and-actions/contexts#needs-context
something like this:

send-notification:
  name: Send Notification
  runs-on: ubuntu-latest
  needs: [update-automation, create-pr]
  if: ${{ success() && needs.create-pr.result == 'success' }}

[vpaiu]

Removed the redundant variable in the new commit.