doc: samples: added documentation for new radio_test hopping_sequence command

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

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

Author: thomas-m-johansen

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

@@ -343,6 +343,8 @@ Peripheral samples
 
   * Added the new ``start_tx_sweep_with_sleep`` shell command.
     It allows for running a TX sweep with silent periods between each frequency.
+  * Added the new ``tx_with_sleep_custom_hopping_sequence_set`` shell command.
+    It allows for setting a custom channel sequence for the ``start_tx_sweep_with_sleep`` command.
 
 PMIC samples
 ------------

samples/peripheral/radio_test/README.rst

@@ -142,6 +142,9 @@ User interface
      - <tx output power>
      - Set total output power in dBm.
        This value includes SoC output power and front-end module gain.
+   * - tx_with_sleep_custom_hopping_sequence_set
+     - <sequence of up to 80channels>
+     - Set a custom sequence for the start_tx_with_sleep command
 
 TX output power
 ===============