Add package loading test

Author: Joseph-Edwards

.github/workflows/tests.yml

@@ -57,6 +57,8 @@ jobs:
       - name: "Pip installing libsemigroups_pybind11 . . ."
         run: |
           CXX="${{ matrix.compiler }}" python -m pip install . -v
+      - name: "Test package loading . . ."
+        run: python -c "from libsemigroups_pybind11 import *"
       - name: "python -m pytest -vv tests/test_*.py . . ."
         run: |
           python -m pytest -vv tests/test_*.py