samples: ipsp: add a debug config build example

Add an example referring to the (already existing) prj_dbg.conf config.

Signed-off-by: Fabio Baltieri <[email protected]>

Author: fabiobaltieri

samples/bluetooth/ipsp/README.rst

@@ -22,6 +22,16 @@ Sample can be built and executed for the nRF52840 DK NRF52840 as follows:
    :goals: build flash
    :compact:
 
+To build a debug version, with logging and shell support, use the config file
+:file:`prj_dbg.conf`:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/bluetooth/ipsp
+   :board: nrf52840dk_nrf52840
+   :conf: prj_dbg.conf
+   :goals: build flash
+   :compact:
+
 Building and Running for Linux kernels released before 4.12
 ===========================================================
 .. note::