include: Added a tiny bit to SDL_sensor.h's category documentation.

Reference Issue #11847.

include/SDL3/SDL_sensor.h

@@ -24,6 +24,8 @@
  *
  * SDL sensor management.
  *
+ * These APIs grant access to gyros and accelerometers on various platforms.
+ *
  * In order to use these functions, SDL_Init() must have been called with the
  * SDL_INIT_SENSOR flag. This causes SDL to scan the system for sensors, and
  * load appropriate drivers.