ci: pin third-party GitHub Actions to commit SHAs

Author: ReneWerner87

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
   Linter:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           fetch-depth: 0
       - run: npx awesome-lint