CI: Run library checks

Author: ubruhin

.github/workflows/main.yml

@@ -8,4 +8,4 @@ jobs:
       options: --entrypoint /bin/bash
     steps:
     - uses: actions/checkout@v1
-    - run: librepcb-cli open-library --all --strict --minify-step .
+    - run: librepcb-cli open-library --all --strict --check --minify-step .