Make generator task runner agnostic #2
Description
Once the CLI can build without any cooperation from the app (arch-js/arch-cli#4) we can remove all task runner handling from the generator and not require a task runner at all.
The reasoning behind it is you shouldn't need a task runner to compile a Reflex app and if you do use one, you should integrate reflex build into it, not run the build from it. That way we can change the build step and not ask people to upgrade. We're also not opinionated about supported task runners.
We can still easily use gulp behind the scenes to do reflex build.