Add script to run {N} in preview mode

[dungahk]

Description

Sometimes I use the preview feature of {N} to quickly preview the app in my smartphone, especially when I don't have an emulator configure or when I don't have a cable to connect my smartphone to my laptop and the preview is a quick way to start things off.

How

Add an npm script to package.json:

{
  "start.nativescript.app.preview": "cd apps/nativescript-${appName} && tns preview --hmr"
}

Where in the code

https://github.com/nstudio/xplat/blob/master/src/app.nativescript/index.ts#L56