Sync SDL3 wiki -> header

include/SDL3/SDL_properties.h

@@ -22,7 +22,26 @@
 /**
  * # CategoryProperties
  *
- * SDL properties.
+ * A property is a variable that can be created and retrieved by name at
+ * runtime.
+ *
+ * All properties are part of a property set (SDL_PropertiesID). A property
+ * set can be created with the SDL_CreateProperties function and destroyed
+ * with the SDL_DestroyProperties function.
+ *
+ * Properties can be added to and retrieved from a property set through the
+ * following functions:
+ *
+ * - SDL_SetProperty and SDL_GetProperty operate on `void*` pointer types.
+ * - SDL_SetStringProperty and SDL_GetStringProperty operate on string types.
+ * - SDL_SetNumberProperty and SDL_GetNumberProperty operate on signed 64-bit
+ *   integer types.
+ * - SDL_SetFloatProperty and SDL_GetFloatProperty operate on floating point
+ *   types.
+ * - SDL_SetBooleanProperty and SDL_GetBooleanProperty operate on boolean
+ *   types.
+ *
+ * Properties can be removed from a set by using SDL_ClearProperty.
  */