Update README.md

Added https://sovransystems.com that uses RTL based on (https://github.com/fort-nix/nix-bitcoin).

.github/README.md

@@ -35,6 +35,7 @@ RTL is available on the below platforms/services:
 * [BCubium](https://bgeometrics.com)
 * [Start9Labs](https://start9labs.com)
 * [Umbrel](https://github.com/getumbrel/umbrel)
+* [Sovran Systems](https://sovransystems.com)
 
 Docker Image: https://hub.docker.com/r/shahanafarooqui/rtl