Add a command to add or remove platform

[Zagrios]

Hi,
Maybe I've missed something, but adding or removing a target platform after the first initialization of the project is painful.
We need to modify several JSON packages and ensure that we haven't introduced a typo or made some other mistakes.

It would be really convenient to have a command like napi platform --add "platform_name" or simply napi platform, and then be able to select or deselect a platform from the CLI, something like this: