feat: add led plugging tool to readme

README.md

@@ -51,12 +51,28 @@ export ESP32_WPA2_PSK=the-wifi-psk
 pio run -t upload
 ```
 
+### led_plugging_tool/
+
+A 3D-printable tool that helps with cutting the LED legs to size and attach them to JST ZH-4 connectors the correct way.
+
+Usage:
+
+1. Print the tool on a 3D printer.
+2. Put a LED bulb-first into the tool hole.  Especially on first use, make sure that it's all the way in.
+    - The LED should only fit in one orientation.
+3. Use a pair of wire cutters to cut the LED legs as close to the tool's surface as possible.
+4. Take a cable fitted with JST ZH-4 connectors and push one connector firmly onto the LED legs inside the tool.
+    - The connector, too, should only (fully) fit in one orientation.
+	- You may need to bend the LED legs a little to get them to a pitch close enough to 1.5mm that the connector will slide on.
+5. Pull the cable to remove the connector and LED from the tool.
+6. Repeat steps 2-5 for every LED you need to prepare.
+
 ## Components
 
 - WS2812-compatible 5mm bulb LEDs: https://de.aliexpress.com/item/1005005003701575.html
 - Black 5mm LED sockets: https://de.aliexpress.com/item/1005005062684329.html
 - ESP32-C3 Super Mini: https://de.aliexpress.com/item/1005006252882434.html
-- JST-ZH cables: https://de.aliexpress.com/item/1005007298855435.html
+- JST-ZH cables: https://de.aliexpress.com/item/1005007298855435.html (4P, Reversed)
 
 
 [spaceapi]: https://spaceapi.io