title: Webpack warning when upgrading Angular 6
body: <p>I upgraded Angular from version 6.0.0 to 6.1.3. After running <code>ng update @angular/core</code> I got the following warning:</p>
  
  <pre><code>npm WARN @ngtools/webpack@6.0.8 requires a peer of typescript@~2.4.0 || 
  ~2.5.0 || ~2.6.0 || ~2.7.0 but none is installed. You must install 
  peer dependencies yourself.
  </code></pre>
  
  <p>What is the meaning of <code>peer of typescript</code> ? According to <code>ng -version</code>, typescript is installed. What's the version <code>@ngtools/webpack</code>  is looking for?</p>
  
  <p>ng -version:</p>
  
  <pre><code>Angular CLI: 6.1.4
  Node: 8.9.1
  OS: win32 x64
  Angular: 6.1.3
  ... animations, common, compiler, compiler-cli, core, forms
  ... http, language-service, platform-browser
  ... platform-browser-dynamic, router
  
  Package                           Version
  -----------------------------------------------------------
  @angular-devkit/architect         0.6.8
  @angular-devkit/build-angular     0.6.8
  @angular-devkit/build-optimizer   0.6.8
  @angular-devkit/core              0.6.8
  @angular-devkit/schematics        0.7.4
  @angular/cli                      6.1.4
  @ngtools/webpack                  6.0.8
  @schematics/angular               0.7.4
  @schematics/update                0.7.4
  rxjs                              6.2.2
  typescript                        2.9.2
  webpack                           4.8.3
  </code></pre>