boards: nrf52840_mdk_usb_dongle: Improve documentation

- Fix typo in SoC name (nRF5240 -> nRF52840)
- Use bullet lists for better readability
- Add link to a readable pinout diagram

Signed-off-by: Manoel Brunnen <manoel.brunnen@orgatex.de>

Author: oxmb

boards/makerdiary/nrf52840_mdk_usb_dongle/doc/index.rst

@@ -3,24 +3,40 @@
 Overview
 ********
 
-The nRF52840 MDK USB Dongle is a small and low-cost development platform enabled
-by the nRF5240 multiprotocol SoC in a convenient USB dongle form factor.
+The nRF52840 MDK USB Dongle is a small and low-cost development platform
+enabled by the nRF52840 multiprotocol SoC in a convenient USB dongle
+form factor.
 
-The design features a programmable user button, RGB LED, up to 12 GPIOs and 2.4G
-Chip antenna on board. It can be used as a low-cost
-Bluetooth5/Tread/802.15.4/ANT/2.4GHz multiprotocol node or development
-board. Alternatively the USB Dongle can be used as a Network Co-Processor(NCP)
-with a simple connection to a PC or other USB enabled device.
+Hardware
+********
+
+The design features:
+
+* Programmable user button
+* RGB LED
+* Up to 12 GPIOs
+* 2.4 GHz chip antenna
 
-See `nrf52840-mdk-usb-dongle website`_ for more information about the development
-board and `nRF52840 website`_ for the official reference on the IC itself.
+The USB Dongle can be used as:
 
+* A low-cost Bluetooth 5/Thread/802.15.4/ANT/2.4GHz multiprotocol node
+* A development board
+* A Network Co-Processor (NCP) with a simple connection to a PC or other USB enabled device
+
+For more information:
+
+* See the `nrf52840-mdk-usb-dongle website`_ for details about the development board
+* See the `nRF52840 website`_ for the official reference on the IC itself
+* See the `nrf52840-mdk-usb-dongle pinout diagram`_ for details about the pin usage of the board
 
 References
 **********
+
 .. target-notes::
 
 .. _nRF52840 website:
    https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF52840
 .. _nrf52840-mdk-usb-dongle website:
    https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/
+.. _nrf52840-mdk-usb-dongle pinout diagram:
+    https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/assets/attachments/nrf52840-mdk-usb-dongle-pinout_v1_1.pdf