docs: stepper: add stepper stop function

- **Move to** a specific position also known as **absolute movement** using :c:func:`stepper_move_to`.

- Run continuously with a **constant step interval** in a specific direction until

  a stop is detected using :c:func:`stepper_run`.

- **Stop** the stepper using :c:func:`stepper_stop`.

- Check if the stepper is **moving** using :c:func:`stepper_is_moving`.

- Register an **event callback** using :c:func:`stepper_set_event_callback`.