Add GET BB_LABEL function and docs (#569)

* Add GET BUNNY_LABEL to get.sh

Instead of hardcoding "BashBunny" or whatever new name the Bunny has, attackers can use a GET command.

* Add docs for GET HOST_IP & GET BB_LABEL

payloads/extensions/get.sh

@@ -26,6 +26,10 @@ function GET() {
       [[ "${ScanForOS,,}" == *"linux"* ]] && export TARGET_OS='LINUX' && return
       export TARGET_OS='UNKNOWN'
       ;;
+      "BB_LABEL")
+      export BB_LABEL=$(ls -l /dev/disk/by-label/ | awk '/nandf$/ { print $9 }')
+      ;;
+
   esac
 }