James h65 patch mechanicals (raspberrypi#850)

* Update README.md

* Add files via upload

Author: JamesH65

hardware/raspberrypi/mechanical/PoE_HAT_Mechanical.pdf

@@ -1,6 +1,10 @@
 # Mechanical Drawings
 
-## Raspberry Pi 3
+## Raspberry Pi 3B+
+
+- [PDF](rpi-3bplus_mechanical.pdf)
+
+## Raspberry Pi 3B
 
 - [PDF](Raspberry-Pi-3B-V1.2-Mechanical.pdf)
 - [DXF](Raspberry-Pi-3B-V1.2-Mechanical.dxf)
@@ -13,3 +17,9 @@
 ## Raspberry Pi Zero (v1.2)
 
 - [PDF](Raspberry-Pi-Zero-V1.2-Mechanical.pdf)
+
+## Raspberry Pi PoE HAT
+
+- [PDF](PoE_HAT_Mechanical.pdf)
+
+