Add connection diagram for weedo tina2 (#752)

* add a wiki page about TINA2 printer

* add into sidebar

Author: atsju

wiki/Weedo-Tina2.md

@@ -0,0 +1,10 @@
+# Where to connect on Weedo Tina2 (Mega2560 based)
+
+This printer is also brand labelled as **Monoprice MP cadet 3D printer**
+
+![Weedo Tina2 connection diagram](https://raw.githubusercontent.com/wiki/luc-github/ESP3D/images/TINA2/weedo_tina2.jpg)
+
+In marlin this connection is **serial port 3**.
+
+Note the Mega2560 is 5V powered and ESP is 3V3 powered.  
+Internet in controversial but it seems that ESP32 is 5V tolerant on input pins so it should not be an issue.  

wiki/_Sidebar.md

@@ -25,6 +25,7 @@
 * [Smoothieboard](https://github.com/luc-github/ESP3D/wiki/Smoothieboard)
 * [Anycubic i3 mega - Trigorilla 8bit](https://github.com/luc-github/ESP3D/wiki/Trigorilla)
 * [Anet A8](https://github.com/luc-github/ESP3D/wiki/How-to-connect-on-ANET-A8)
+* [Weedo Tina2](https://github.com/luc-github/ESP3D/wiki/Weedo-Tina2)
 
 ### ESP daughterboard wiring