cascadia-code: add ryanccn as maintainer

pkgs/data/fonts/cascadia-code/default.nix

···
     homepage = "https://github.com/microsoft/cascadia-code";
     changelog = "https://github.com/microsoft/cascadia-code/raw/v${version}/FONTLOG.txt";
     license = licenses.ofl;
-    maintainers = [ ];
+    maintainers = with maintainers; [ ryanccn ];
     platforms = platforms.all;
   };
 }