weechat: point description to documentation

pkgs/applications/networking/irc/weechat/default.nix

@@ -72,6 +72,11 @@ let
       meta = {
         homepage = http://www.weechat.org/;
         description = "A fast, light and extensible chat client";
+        longDescription = ''
+          You can find more documentation as to how to customize this package
+          (eg. adding python modules for scripts that would require them, etc.)
+          on https://nixos.org/nixpkgs/manual/#sec-weechat .
+        '';
         license = stdenv.lib.licenses.gpl3;
         maintainers = with stdenv.lib.maintainers; [ lovek323 garbas the-kenny lheckemann ];
         platforms = stdenv.lib.platforms.unix;