Add Feitian OpenSK USB Dongle (#257) (#258)

Co-authored-by: superskybird <skybird.le@gmail.com>

Co-authored-by: Geoffrey <geoffrey@ftsafe.com>
Co-authored-by: superskybird <skybird.le@gmail.com>

Author: 3 people

docs/install.md

@@ -17,6 +17,7 @@ You will need one the following supported boards:
 *   [Nordic nRF52840 Dongle](https://www.nordicsemi.com/Software-and-tools/Development-Kits/nRF52840-Dongle)
     to have a more practical form factor.
 *   [Makerdiary nRF52840-MDK USB dongle](https://wiki.makerdiary.com/nrf52840-mdk/).
+*   [Feitian OpenSK dongle](https://feitiantech.github.io/OpenSK_USB/).
 
 In the case of the Nordic USB dongle, you may also need the following extra
 hardware: