gn: add marcin-serwin to maintainers

Signed-off-by: Marcin Serwin <marcin@serwin.dev>

+1
+1
pkgs/by-name/gn/gn/package.nix
··· 88 maintainers = with lib.maintainers; [ 89 stesie 90 matthewbauer 91 ]; 92 }; 93 }
··· 88 maintainers = with lib.maintainers; [ 89 stesie 90 matthewbauer 91 + marcin-serwin 92 ]; 93 }; 94 }