Update example code in README to note the difference of event type sw…

…itch case between `master` and `v0.4.x`

Signed-off-by: Lilis Iskandar <[email protected]>

README.md

@@ -93,7 +93,7 @@ func main() {
 	for running {
 		for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
 			switch event.(type) {
-			case sdl.QuitEvent:
+			case sdl.QuitEvent: # NOTE: Please use `*sdl.QuitEvent` for `v0.4.x` (current version).
 				println("Quit")
 				running = false
 				break