add demo

Author: cedvdb

.github/workflows/tests.yml

@@ -33,7 +33,7 @@ jobs:
 
       # Consider passing '--fatal-infos' for slightly stricter analysis.
       - name: Analyze project source
-        run: dart analyze
+        run: dart analyze lib test example
 
       # Your project will need to have tests in test/ and a dependency on
       # package:test for this step to succeed. Note that Flutter projects will