Ft live reload files

[brayovsky]

Adds a watch script to rebuild files while editing.
Just a proposal no need to merge first.

Fix to issue #16

[brayovsky]

@adamwatters I added a script instead of ejecting the app. However the build is still too slow to be practical and I can't figure why. It builds the src/ folder. However, the commented lines in scripts/watch.js could also build ext-src upon edit. What do you think? I'd like some help on optimising the script to be faster and also build ext-src while not using child_process.exec as it adds more time to the build.

[adamwatters]

awesome! i’ll take a look at this later today 👍