title: dropdown toggle issue in navbar with ng-bootstrap (4) angular 2 (cli)
body: <p>I followed the instructions described <a href="https://ng-bootstrap.github.io/#/getting-started" rel="noreferrer">here</a> and css is working perfectly. For the dropdown toggle I used this code</p>
  
  <pre><code>&lt;nav class="navbar navbar-light bg-faded"&gt;
    &lt;a class="navbar-brand" href="#"&gt;Navbar&lt;/a&gt;
    &lt;ul class="nav navbar-nav"&gt;
      &lt;li class="nav-item active"&gt;
        &lt;a class="nav-link" href="#"&gt;Home &lt;span class="sr-only"&gt;(current)&lt;/span&gt;&lt;/a&gt;
      &lt;/li&gt;
      &lt;li class="nav-item"&gt;
        &lt;a class="nav-link" href="#"&gt;Link&lt;/a&gt;
      &lt;/li&gt;
      &lt;li class="nav-item"&gt;
        &lt;a class="nav-link" href="#"&gt;Link&lt;/a&gt;
      &lt;/li&gt;
      &lt;li class="nav-item dropdown"&gt;
        &lt;a class="nav-link dropdown-toggle" href="#" id="supportedContentDropdown" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"&gt;Dropdown&lt;/a&gt;
        &lt;div class="dropdown-menu" aria-labelledby="supportedContentDropdown"&gt;
          &lt;a class="dropdown-item" href="#"&gt;Action&lt;/a&gt;
          &lt;a class="dropdown-item" href="#"&gt;Another action&lt;/a&gt;
          &lt;a class="dropdown-item" href="#"&gt;Something else here&lt;/a&gt;
        &lt;/div&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
    &lt;form class="form-inline float-xs-right"&gt;
      &lt;input class="form-control" type="text" placeholder="Search"&gt;
      &lt;button class="btn btn-outline-success" type="submit"&gt;Search&lt;/button&gt;
    &lt;/form&gt;
  &lt;/nav&gt;
  </code></pre>
  
  <p>But the dropdown toggle is not working, although I include NgbModule for Root. Please me know if I had to include something else in my component providers array or anything else. 
  Thanks in advance</p>