title: NGXS @Select usage with state model
body: <p>When using an NGXS <code>@Select</code> decorator what is the right way to access properties defined on the state model.</p>
  
  <p>E.g with the following state defined:</p>
  
  <pre><code>export interface UserStateModel {
   firstname: string;
   lastname: string;
  }
  
  @State&lt;UserStateModel&gt;({
    name: 'user',
    defaults: {}
  })
  export class UserState {..}
  </code></pre>
  
  <p>In a component if I want to select the user state like this:</p>
  
  <pre><code>..export class MyComponent {
  
    @Select(UserState) user$: Observable&lt;UserState&gt;;
  
     ngOnInit(){
       this.user$.subscribe(u =&gt; {
           //do something with user state
           console.log(u.firstname);
       });
     }   
  }
  </code></pre>
  
  <p>I get typescript errors as the <code>firstname</code> property doesn't exist on <code>UserState</code> (as it's defined on the related model type). If I'm referencing the property in the component html template then I don't have any issue.</p>
  
  <p>There is a <a href="https://github.com/ngxs/store/issues/160" rel="noreferrer">related discussion</a> around selector usage but I just want to confirm what I should expect with the current version (and if I'm doing this correctly!).</p>
  
  <p>I'm using <code>"@ngxs/store": "^3.0.0-rc.2",</code></p>