Add Different Preview Options To The Designer

This project is related to Designer which will introduce new theme styles preview option in App Inventor when the Device Default option is clicked. Through this option we can preview how our app will look like on different Android Platforms as well as iOS. The preview options is divided into three categories: Android Holo which is (Android 3.0-4.4.2), Android Material which is (Android 5+) and finally iOS version. Implementing the look and feel of these categories would provide users an idea of how their app would look and work on different platforms.