ci: configure renovate to manage GitHub workflow updates

Update renovate config to allow GitHub workflow updates

Author: alan-agius4

renovate.json

@@ -16,7 +16,8 @@
     "WORKSPACE",
     "package.json",
     "packages/**/package.json",
-    "tests/legacy-cli/e2e/ng-snapshot/package.json"
+    "tests/legacy-cli/e2e/ng-snapshot/package.json",
+    ".github/workflows/**/*.yml"
   ],
   "packageRules": [
     {