security: harden workflow — permissions, pin deps, pin actions

Author: NellInc

.github/workflows/update-footer-year.yml

@@ -13,7 +13,7 @@ jobs:
   update-year:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
         with:
           token: ${{ secrets.GITHUB_TOKEN }}