Add Solo to Readme

[s00500]

Successfully tested with
manufacturer = "SoloKeys", product = "Solo 3.0.0", vid = 0xa2ca, pid = 0x0483
version: U2F_V2
Implements Wink: Yes (Blue Blink)

https://solokeys.com/

Tested with the "Somu" version
on macOS Catalina

Thanks for the nice work =D