add pic of the board

Author: f18m

README.md

@@ -67,6 +67,9 @@ Its main characteristics are:
   * 5V DC power supply terminal
   * 8 relay channels, both NC and NO contacts available
 
+<img title="Relay board" alt="Relay board" src="images/esp-relay-board.png">
+
+
 * 220V to 5V power adapter (5W), [bought on Aliexpress](https://it.aliexpress.com/item/1005006981553550.html?spm=a2g0o.order_list.order_list_main.47.45de36964bR8Kp&gatewayAdapt=glo2ita) (4€ in Oct 2025)
 
 * Temperature sensors, bought on Aliexpress (few € in Oct 2025)