Expose a way for the CLI to set ReactInstanceSettings

[kmelmon]

CLI-created apps have the ability to setup the react instance with settings via ReactInstanceSettings. These settings control various behaviors such as enabling live reload, setting a debug host, etc.

Currently you need to modify the native code to set these and rebuild. It would be nice if there was a way to plumb through ReactInstanceSettings via the CLI.

[kmelmon]

@vmoroz you were also asking about adding this capability, and the requirements may change with the introduction with the ReactApplication and ReactNativeHost. Feel free to add your thoughts!

[kmelmon]

There is now an example of how to do this:
#4531
I consider this enough to call this issue resolved. Closing