wireguard-go: add winter to maintainers

The current maintainers seem to be inactive, and I'm willing to step in
and keep this package alive. :)

Author: winterqt

pkgs/by-name/wi/wireguard-go/package.nix

@@ -68,6 +68,7 @@ buildGoModule (
       license = licenses.mit;
       maintainers = with maintainers; [
         kirelagin
+        winter
         zx2c4
       ];
       mainProgram = "wireguard-go";