Add cap for asteroid spawn delay

Added a minimum amount of time between spawning asteroids. Don't know
how well it'll hold up in plays, but it seems like it should be a good
number.

Scripts/AsteroidSpawn.gd

@@ -7,9 +7,12 @@ var deltaSpawnTime = 1
 
 func _process(delta):
 	spawnTime = 500/get_viewport_rect().size.x * deltaSpawnTime
+	print(spawnTime)
+	print(get_viewport_rect().size.x)
 	time += delta
 	if time > spawnTime:
 		time = 0
+		if spawnTime > 300/get_viewport_rect().size.x:
 			deltaSpawnTime *= 0.995
 		if has_node("Rocket"):
 			var asteroid = asteroidObj.instance()