update workflow and pin dependencies

Author: pxpm

.github/workflows/add-to-project.yml

@@ -14,7 +14,7 @@ jobs:
     name: Add new bugs and PRs to This Week project
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/add-to-project@main
+      - uses: actions/add-to-project@5afcf98fcd03f1c2f92c3c83f58ae24323cc57fd # v2.0.0
         with:
           project-url: https://github.com/orgs/Laravel-Backpack/projects/13
           github-token: ${{ secrets.ADD_TO_PROJECT_PAT }}