title: Scroll position restoration for child root
body: <p>I'm having a problem to get back to a particular scroll position.
  There is a list of lazy-loaded objects in my ObjectListComponent, once I click on the Object name I can check its details. There is a return button, which leads to a previous page with the list of Objects. The problem is that ObjectListComponent is being init from the start and I cannot get back to a previous state, the one before I checked a particular object's details. I need to have my scrollable list of objects and, if I enter ObjectComponent in order to check its details and want to go back to the list, I land on the ObjectList in the very same place my single object is, so I could scroll down and get more objects loaded. </p>
  
  <p>There is an option like 
  RouterModule.forRoot(
    appRoutes,
    { scrollPositionRestoration: 'disabled' } // &lt;-- HERE
  )</p>
  
  <p>But I have RouterModule.forChild and it doesn't accept extra options as an argument.</p>