Re-add mechanical design files

README.md

@@ -7,6 +7,11 @@ Features:
 ![Mounted PCB](/photos/mounted_front.jpg)
 ![3D Render of the PCB](/export/catear_pcb.png)
 
+# 3D Printing
+* The design file should be printed as is and mirrored, to make two ears
+* The PCB is symmetrical and will fit in both ears
+* The battery compartment fits a 803040 single cell lipo
+
 # Program with the Arduino IDE
 Install a few things to get it to work. Ther versions listed here are the ones which were used for testing. Any other later version should work as well
 * The **Arduino IDE** [1.8.13]