Plugin routes don't support RouteConfig

[deer]

I wanted to create a special partials route to load just the right content and expose that with a plugin. Sad times when I spent too much time debugging why the _app wrapper was getting included, even though I clearly had the following in my route:

export const config: RouteConfig = {
  skipAppWrapper: true,
  skipInheritedLayouts: true,
};

Eventually I realized that PluginRoute is missing something like config?: RouteConfig;, and so of course it wasn't being used.