README: add ESP32 URL.

2021-06-15 13:04:36 +01:00 · 2021-06-15 13:04:36 +01:00 · a22adfd3d3
commit a22adfd3d3
--- a/README.md
+++ b/README.md
@ -102,7 +102,8 @@ Various tools are available to manage the device's storage via USB. I use
 ## 2.1 ESP32

 Pinout diagram for the reference board with notes and warnings about reserved
-pins etc. See [this doc](./ESP32/ESP32-Devkit-C-pinout.pdf).
+pins etc. See [this doc](./ESP32/ESP32-Devkit-C-pinout.pdf). See also this
+excellent [resource](https://randomnerdtutorials.com/esp32-pinout-reference-gpios/).

 ## 2.2 SSD1306