Add simple import test to build script

.github/workflows/test-build.yaml

@@ -24,4 +24,6 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -r requirements/${{ matrix.requirements-file }}.txt
-          pip install .
+          pip install .
+      - name: Test import
+        run: python -c "import sgm"