Move OS module out of backend Javascript into a proper module file. Add normal bytearray to bytearray module. Add read:to method to os module for reading into a bytearray.

#{
	main <- {
		foo <- :n {
			if: n < 10 {
				true
			} else: {
				foo <- :n { n }
			}
			foo: n + 1
		}
		print: (string: (foo: 0))
	}
}