doc: samples: added documentation for the new radio_test command

added documentation for the new radio_test command as well as a
changelog entry

Signed-off-by: Thomas Johansen <thomas.johansen@nordicsemi.no>

Author: thomas-m-johansen

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -329,7 +329,10 @@ nRF5340 samples
 Peripheral samples
 ------------------
 
-|no_changes_yet_note|
+* :ref:`radio_test` sample:
+
+  * Added the new ``start_tx_sweep_with_sleep`` shell command.
+    It allows for running a TX sweep with silent periods between each frequency.
 
 PMIC samples
 ------------

samples/peripheral/radio_test/README.rst

@@ -129,6 +129,9 @@ User interface
    * - time_on_channel
      - <time>
      - Time on each channel in ms (between 1 and 99).
+   * - start_tx_sweep_with_sleep
+     - <tx_time> (us) <sleep_time> (us)
+     - Start TX sweep with a controlled sleep cycle
    * - toggle_dcdc_state
      - <state>
      - Toggle DC/DC converter state.