Object.assign not supported with old versions of webview

[bradjc]

Not sure if you care or if this is important, but this line: https://github.com/lab11/summon/blob/master/mobile-app/src/plugins/cordova-plugin-bluetooth/bluetooth.js#L137 breaks with older (perhaps really old) versions of android's webview. I get this error:

I/chromium(17261): [INFO:CONSOLE(145)] "Uncaught TypeError: Object.assign is not a function", source: file:///android_asset/www/plugins/cordova-plugin-bluetooth/bluetooth.js (145)

This probably doesn't matter, but good FYI if you are ever trying to support older devices.