Gin theme compatibility

It seems implementing hook_gin_content_form_routes() solves the problem.

Please register all the new routes with this hook.

As a quick workaround, the hook can be used in a custom module as:

function mymodule_gin_content_form_routes() {
  return [
    'entity.node.edit_form.myformmode',
  ];
}

Thank you, this works while editing entities, but there is still a problem when using /node/add-list/[CUSTOM_FORM_MODE] (which is problematic on its own and I'm trying to get rid of anyway, at least of the button links at /admin/content 😇