Add pull request and id-token write permissions to publish.yaml (#2595)

This is needed in order for packages to be published.

Author: srujzs

Diff for: .github/workflows/publish.yaml

@@ -15,3 +15,6 @@ jobs:
     uses: dart-lang/ecosystem/.github/workflows/publish.yaml@main
     with:
       sdk: dev
+    permissions:
+      id-token: write
+      pull-requests: write