docs: add tcp WSL hint

Author: stefanvogel

platformio.ini

@@ -102,8 +102,8 @@ extra_scripts =
     post:./scripts/copy_webots_shared_libs.py
 
 ; Custom options (https://docs.platformio.org/en/latest/scripting/examples/platformio_ini_custom_options.html)
-custom_webots_ip_address = 127.0.0.1 ; IP address of the Webots simulation, which is used for TCP communication
 custom_webots_protocol = ipc ; [ipc|tcp] - ipc is faster but only works on the same machine, tcp works also over network
+custom_webots_ip_address = 127.0.0.1 ; IP address of the Webots simulation (only used for TCP protocol). Under WSL run 'ip route show | grep default' to find out.
 custom_webots_robot_name = ZumoComSystem
 custom_webots_robot_serial_rx_channel = 4
 custom_webots_robot_serial_tx_channel = 3