Demo app to test UTM integration in Flutter

Urchin Tracking Module (UTM) parameters are five variants of URL parameters used by marketers to track the effectiveness of online marketing campaigns across traffic sources and publishing media. They were introduced by Google Analytics' predecessor Urchin and, consequently, are supported out-of-the-box by Google Analytics. The UTM parameters in a URL identify the campaign that refers traffic to a specific website, and attributes the browser's website session and the sessions after that until the campaign attribution window expires to it. The parameters can be parsed by analytics tools and used to populate reports.