Support and comparability with NativeScript 6

[Izrab]

Support and comparability with NativeScript version 6, in other words, support for AndroidX, webpack workflow, and NS6 stack (i.e. `tns-core-modules 6, tns-android 6, dev webpack 6, etc.etc)

[shiv19]

@Izrab
This plugin in its current state already works with {N} 6, thanks to JIT,
but if you want to use the AndroidX version of this plugin's lib, it is available here
https://npm.proplugins.org/-/web/detail/@proplugins/nativescript-cfalert-dialog

Any PRs to this repo are welcome :)