Create an .md file for the YuPiF4

An .md file to describe the YuPiF4 target was created in the Doc/ folder of the Inav project.

docs/Board - YuPiF4.md

@@ -0,0 +1,38 @@
+# YuPiF4 by RcNet
+
+An high quality flight controller for the most demanding pilotes.
+
+## Description
+
+The YuPiF4 is a 36x36mm (30.5x30.5 mounting holes) board with an F4 microcontroller.
+
+## MCU, Sensors and Features
+### Hardware  
+- MCU: STM32F405RTG6  
+- IMU: not yet defined  
+- IMU Interrupt: Yes  
+- BARO: No  
+- VCP: Yes  
+- Hardware UARTS: 3 with an inverter for SBus and a Smart-Port Pad to solder directly your SPort wire  
+- Blackbox: SD card slot  
+- PPM : A specific pad is available for PPM input  
+- Battery Voltage Sensor: Yes, directly connected, no wiring necessary  
+- Integrated Voltage Regulator: the board can be powered by your lipo (2S to 6S)  
+- Brushed Motor Mosfets: No  
+- Motor outputs : can drive up to 6 motors  
+- Buttons: Boot0 to enter in DFU mode### Features  
+- Current Sensor: Not implemented  
+- BlHeli passthrough: Yes   
+- WS2811 Led Strip: Yes (on motor output Pin 5)  
+- Transponder: No
+
+### Extension Board
+- An extension board with a GPS and a Baro will be available
+
+## Designers and Maintainers
+
+[RcNet](https://github.com/ted-rcnet) and [FaduF](https://github.com/Faduf)
+
+## Manufacturers and Distributors
+
+This board is currently in the prototype phase. Only small batches were manufactured for testing.Website : http://www.yupif4.com/