title: AddViewLocalization on IServiceCollection no longer exists
body: <p>this should be a simple one. I'm tring to run AddViewLocalization and AddDataAnnotationsLocalization on an <em>IServiceCollection</em>, but am getting </p>
  
  <blockquote>
    <p>"'IServiceCollection' does not contain a definition for
    'AddViewLocalization' and the best extension method overload
    'MvcLocalizationMvcBuilderExtensions.AddViewLocalization(IMvcBuilder,
    LanguageViewLocationExpanderFormat, Action)'
    requires a receiver of type 'IMvcBuilder'"</p>
  </blockquote>
  
  <p>The code:</p>
  
  <pre><code>    services.AddLocalization(o =&gt;
      {
          o.ResourcesPath = Const.LocalizationResourcePath;
      })
          .AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix, options =&gt; options.ResourcesPath = Const.LocalizationResourcePath)
          .AddDataAnnotationsLocalization();
  </code></pre>
  
  <p>this worked just fine before updating to asp.net core 2.1</p>
  
  <p>what assembly do I need to reference?</p>