Add a note that the example is written in old style

Author: Mikolaj

README.md

@@ -27,6 +27,9 @@ A small example executable is included with the library. It loads a given font
 and uses it to display text in various ways. You can find it in the `example`
 directory.
 
+Note: this example works, but is written in sdl1-style, so instead
+you should change surfaces to textures and follow the usual sdl2 API.
+
 ```bash
 cd sdl2-ttf
 cabal configure -fexample

example/Example.hs

@@ -1,3 +1,8 @@
+-- Note: this code uses the old, inherited from sdl1, surface-based
+-- API for displaying on screen. It can't be used together with the new
+-- renderer API. You should instead copy the surface to a texture ASAP
+-- and then display the texture using the renderer in the usual
+-- sdl2 way.
 {-# LANGUAGE LambdaCase        #-}
 {-# LANGUAGE OverloadedStrings #-}