Content: Add MADFLIGHT_FC3 board doc (#622)

* Content: Add MADFLIGHT_FC3 board doc

* add </TabItem>

* typo + img links

* title

* typo

* whitespace

* store link

* title case

Author: qqqlab

docs/wiki/boards/current/MADFLIGHT_FC3/MADFLIGHT_FC3-images/MADFLIGHT_FC3-bottom.png

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+---
+description: MADFLIGHT_FC3
+sidebar_custom_props:
+  specs:
+    target: MADFLIGHT_FC3
+    mcu: RP2350B
+    imu: ICM-45686
+    osd: None, but SPI port and VTX available
+    barometer: BMP390
+    blackbox: MicroSD card
+    dimensions: 50.7x41.6x4.4mm
+    mounting: 30.5x30.5mm
+    weight: 6.3g
+---
+
+import Tabs from '@theme/Tabs'
+import TabItem from '@theme/TabItem'
+import SpecGrid from '@site/src/components/SpecGrid'
+
+# Madflight FC3 RP2350B
+
+<Tabs>
+
+<TabItem value="specifications" label="Specifications" default>
+
+<SpecGrid>
+
+![Top](./MADFLIGHT_FC3-images/MADFLIGHT_FC3-top.png)
+
+</SpecGrid>
+
+## Other Features
+
+{/* List the remaining available features, if a specific feature is not present, write "No" */}
+{/* The format and order of the list should stay the same */}
+
+- SD Card Slot: Yes
+- Onboard Receiver: No
+- Hardware Inverter: No
+- Bluetooth: No
+- WiFi: No
+- Onboard RGB LED: Yes
+
+## Information
+
+:::info
+
+[madflight FC3 Documentation](https://madflight.com/Board-FC3/)
+
+:::
+
+:::info
+
+[madflight FC3 Store](https://www.tindie.com/products/madflight/flight-controller-raspberry-pi-rp2350b/)
+
+:::
+
+## Input/Output
+
+{/* List the available connections accessible from pads or connectors, if a specific connection is not present, write "No" */}
+
+- USB Connector: USB C
+- Motor Outputs: 8x
+- UARTs: 4x (2x hardware, 2x PIO)
+- I2C: Yes
+- SWD: Yes
+- SPI: Yes
+- 3.3V Output: Yes
+- 4.5V (VBUS) Output: No
+- 5V Output: 2A
+- 12V Output: No
+- Current Sensor: Yes
+- Analog RSSI Input: Yes
+- LED Strip Output: Yes
+- Buzzer Output: Yes
+
+## Pads
+
+### UARTs
+
+| Name     | Notes                             |
+| -------- | --------------------------------- |
+| USB VCP  |                                   |
+| UART0    | RC Input                          |
+| UART1    | GPS                               |
+| PIOUART0 | User, ESC Telem, VTX              |
+| PIOUART1 | User, ESC Telem, VTX              |
+
+## Connectors
+
+### 2.54mm Pin Header - First Row
+
+| Pin Number | GPIO | Signal Name |
+| ---------- | ---- | ----------- |
+| 1          | 0    | UART0_TX    |
+| 2          | 1    | UART0_RX    |
+| 3          | 5.0V |             |
+| 4          | GND  |             |
+| 5          | 2    | I2C1_SDA    |
+| 6          | 3    | I2C1_SCL    |
+| 7          | 4    | UART1_TX    |
+| 8          | 5    | UART1_RX    |
+| 9          | 5.0V |             |
+| 10         | GND  |             |
+| 11         | 6    | MOTOR1      |
+| 12         | 7    | MOTOR2      |
+| 13         | 8    | MOTOR3      |
+| 14         | 9    | MOTOR4      |
+| 15         | 3.3V |             |
+| 16         | GND  |             |
+
+### 2.54mm Pin Header - Second Row
+
+| Pin Number | GPIO | Signal Name |
+| ---------- | ---- | ----------- |
+| 1          | 10   | PIOUART0_TX |
+| 2          | 11   | PIOUART0_RX |
+| 3          | 5.0V |             |
+| 4          | GND  |             |
+| 5          | 12   | LED1_PIN    |
+| 6          | 13   | LED2_PIN    |
+| 7          | 14   | PIOUART1_TX |
+| 8          | 15   | PIOUART1_RX |
+| 9          | 5.0V |             |
+| 10         | GND  |             |
+| 11         | 16   | MOTOR5      |
+| 12         | 17   | MOTOR6      |
+| 13         | 18   | MOTOR7      |
+| 14         | 19   | MOTOR8      |
+| 15         | 3.3V |             |
+| 16         | GND  |             |
+
+### 2.54mm Pin Header - Third Row
+
+| Pin Number | GPIO | Signal Name |
+| ---------- | ---- | ----------- |
+| 1          | 20   | unused      |
+| 2          | 21   | unused      |
+| 3          | 5.0V |             |
+| 4          | GND  |             |
+| 5          | 22   | PINIO1_PIN  |
+| 6          | 23   | PINIO2_PIN  |
+| 7          | 24   | PINIO3_PIN  |
+| 8          | 25   | PINIO4_PIN  |
+| 9          | 5.0V |             |
+| 10         | GND  |             |
+| 11         | 40   | ADC_RSSI_PIN |
+| 12         | 41   | ADC_CURR_PIN |
+| 13         | 42   | ADC_EXTERNAL1_PIN |
+| 14         | 43   | unused      |
+| 15         | 3.3V |             |
+| 16         | GND  |             |
+
+</TabItem>
+
+<TabItem value="photos" label="Photos">
+
+![Top](./MADFLIGHT_FC3-images/MADFLIGHT_FC3-top.png)
+
+![Bottom](./MADFLIGHT_FC3-images/MADFLIGHT_FC3-bottom.png)
+
+</TabItem>
+
+</Tabs>
+
+