Add wiring diagram.

README.md

@@ -10,6 +10,8 @@ Heavy lifting (NMEA parsing) provided by [minmea], which is included in this rep
 
 Connect the GPS module to power and the USART using GPIO pins 9 (3.3V), 11 (GND), 13 (TX), and 14 (RX), as appropriate.
 
+![wiring](wiring.png)
+
 ## Building the FAP
 
 1. Clone the [flipperzero-firmware] repository.