title: cmd : react-native run-android on every file change
body: <p>when I run "react-native run-android" The build is deployed to emulator and the program executes fine. But after I make changes to the files locally, I need to run "react-native run-android".</p>
  
  <p>Any way this can be done using watchman, like it happens for react-native ios.</p>
  
  <p>Thanks</p>