👷 fix(ci): add workflow permissions (#21)

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

.github/workflows/assign.yml

@@ -7,6 +7,8 @@ jobs:
   assign:
     if: github.actor == 'dependabot[bot]'
     runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
     steps:
       - name: Assign reviewer
         uses: actions/github-script@v7