Sync SDL3 header -> wiki

SDL3/README/migration.md

@@ -875,7 +875,7 @@ The following functions have been removed:
 
 ## SDL_keycode.h
 
-SDL_Keycode is now an enum instead of Sint32.
+The SDL_KeyCode enum values have been changed to defines to more clearly reflect that they are a subset of the possible values of an SDL_Keycode.
 
 The following symbols have been renamed:
 * KMOD_ALT => SDL_KMOD_ALT

SDL3/SDLK_UNKNOWN.md

@@ -0,0 +1,18 @@
+###### (This is the documentation for SDL3, which is under heavy development and the API is changing! [SDL2](https://wiki.libsdl.org/SDL2/) is the current stable version!)
+# SDLK_UNKNOWN
+
+A subset of possible virtual key values.
+
+## Header File
+
+Defined in [SDL_keycode.h](https://github.com/libsdl-org/SDL/blob/main/include/SDL3/SDL_keycode.h), but apps should use `#include <SDL3/SDL.h>`
+
+## Syntax
+
+```c
+#define SDLK_UNKNOWN    0
+```
+
+----
+[CategoryAPI](CategoryAPI), [CategoryAPIMacro](CategoryAPIMacro)
+

SDL3/SDL_Keycode.md

@@ -23,9 +23,6 @@ the unmodified character that would be generated by pressing the key, or an
 A special exception is the number keys at the top of the keyboard which map
 to [SDLK_0](SDLK_0)...[SDLK_9](SDLK_9) on AZERTY layouts.
 
-The list of `SDLK_*` values are in [SDL_KeyCode](SDL_KeyCode), which is an
-enum, while [SDL_Keycode](SDL_Keycode) is an integer.
-
 ## Version
 
 This datatype is available since SDL 3.0.0.