fix: add copilot-requests to GitHub Actions workflow JSON schema (#18067)

* Initial plan

* fix: add copilot-requests to GitHub Actions workflow JSON schema permissions

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Modify 'copilot-requests' schema definition

Updated 'copilot-requests' schema to include type and enum.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: Copilot

pkg/workflow/schemas/github-workflow.json

@@ -171,6 +171,10 @@
         "checks": {
           "$ref": "#/definitions/permissions-level"
         },
+        "copilot-requests":  {
+          "type": "string",
+          "enum": ["write", "none"]
+        },
         "contents": {
           "$ref": "#/definitions/permissions-level"
         },