python311Packages.plugincode: add changelog to meta

pkgs/development/python-modules/plugincode/default.nix

···
   meta = with lib; {
     description = "Library that provides plugin functionality for ScanCode toolkit";
     homepage = "https://github.com/nexB/plugincode";
+    changelog = "https://github.com/nexB/plugincode/blob/v${version}/CHANGELOG.rst";
     license = licenses.asl20;
     maintainers = [ ];
   };