Add Centreing a surface

Centreing-a-surface.md

@@ -0,0 +1,8 @@
+# Centreing a surface
+`gameUtils.centre(surface, size)` provides an easy way to centre a surface.
+
+## Usage:
+```python
+self.surf.blit(gameUtils.centre(image, self.size), (0, 0))
+```
+This will centre `image` to the middle of the game window.