Support IPv6 ranges in split tunneling

[0xlynett]

Is your feature request related to a problem? Please describe.
I'm trying to use Yggdrasil, which is a mesh network that uses an IPv6 range (0200::/7). I don't want to have to turn off the Windscribe firewall to access it.

Describe the solution you'd like
Adding IPv6 support to Windscribe's split tunneling feature.

Describe alternatives you've considered
Disabling the firewall, but that results in a lot of traffic leaking. I could also just not use Yggdrasil and instead use some other thing such as innernet or Tailscale for connecting my devices.

Additional context
As I'm not familiar w/ the codebase, I'm not sure if this would require many changes across the client and backend or only a few. I know that client/common/utils/ipvalidation.cpp automatically assumes IPv4 in its regex validation.

[jaxu]

Fair enough, added to our dev board.

[bernerdad]

This has been implemented in the 2.13.2 release. Please take it for a spin and let us know if we hit the target. Cheers!