security: pin action reference and restrict permissions

Author: suscripty

.github/workflows/new-issue.yml

@@ -11,8 +11,9 @@ jobs:
   add-to-project:
     name: Add issue to BeeWare project
     runs-on: ubuntu-latest
+    permissions: {}
     steps:
-      - uses: actions/add-to-project@v2.0.0
+      - uses: actions/add-to-project@5afcf98fcd03f1c2f92c3c83f58ae24323cc57fd  # v2.0.0
         with:
           project-url: https://github.com/orgs/beeware/projects/1
           github-token: ${{ secrets.BRUTUS_PAT_TOKEN }}