Improved keycode documentation

include/SDL3/SDL_keycode.h

@@ -45,11 +45,13 @@
  * `SDLK_*` constant for those keys that do not generate characters.
  *
  * A special exception is the number keys at the top of the keyboard which map
- * to SDLK_0...SDLK_9 on AZERTY layouts.
+ * by default to SDLK_0...SDLK_9 on AZERTY layouts.
  *
  * Keys with the `SDLK_EXTENDED_MASK` bit set do not map to a scancode or
  * unicode code point.
  *
+ * Many common keycodes are listed below, but this list is not exhaustive.
+ *
  * \since This datatype is available since SDL 3.2.0.
  *
  * \sa SDL_HINT_KEYCODE_OPTIONS