remove /include/twn_config.h, move defauls to relevant headers

src/twn_input_c.h

@@ -7,6 +7,9 @@
 #include <SDL2/SDL.h>
 
 
+#define KEYBIND_SLOTS_DEFAULT 3
+
+
 union ButtonCode {
     SDL_Scancode scancode;
     SDL_Keycode keycode;