Added test and codecov steps

Author: mvanbeusekom

.github/workflows/google_api_availability.yaml

@@ -54,3 +54,15 @@ jobs:
       - name: Run iOS build
         run: flutter build ios --release --no-codesign
         working-directory: ${{env.example-directory}}
+        
+      # Run all unit-tests with code coverage
+      - name: Run unit tests
+        run: flutter test --coverage
+        working-directory: ${{env.source-directory}}
+
+      # Upload code coverage information
+      - uses: codecov/codecov-action@v1
+        with:
+          file: ${{env.source-directory}}/coverage/lcov.info # optional
+          name: Google API Availability (App Facing Package) # optional
+          fail_ci_if_error: true