adding link to similar Iris Mod

jpconstantineau · web-flow · commit 8642a0dbf705 · 2018-06-02T22:46:33.000-06:00
diff --git a/InstallingExtraKey.md b/InstallingExtraKey.md
@@ -9,3 +9,6 @@ As of V1.02, this empty position has been made accessible on the PCB.
 ![pcb](images/Extra_handwired_key.jpg)
 
 Install D28 and handwire the additional switch to the 2 pin header located near the thumb cluster.
+
+
+This extra key allows a modification to the keyboard similar to this [one](https://imgur.com/a/Vr0oH#H5ut7ZZ) on the Iris.
