doc: added raspberrypi5 to the list of supported machines

Signed-off-by: Jan Vermaete <jan.vermaete@gmail.com>

docs/layer-contents.md

@@ -11,6 +11,7 @@
 * raspberrypi3-64 (64 bit kernel & userspace)
 * raspberrypi4
 * raspberrypi4-64 (64 bit kernel & userspace)
+* raspberrypi5
 * raspberrypi-cm (dummy alias for raspberrypi)
 * raspberrypi-cm3