Add check that the hook is configured for pre-commit in CI (#28)

.github/workflows/ci.yml

@@ -59,6 +59,9 @@ jobs:
       - name: Install testing dependencies
         run: python -m pip install '.[dev]'
 
+      - name: Validate pre-commit hook
+        run: pre-commit try-repo . strip-exif --all-files
+
       - name: Run tests
         run: pytest