message: chore(docs): fixed example code for app.component.html
  The previous example code resulted in broken widget, the fixed code is taken directly from
diff: @@ -113,15 +113,16 @@ import { BsDropdownModule } from 'ngx-bootstrap/dropdown';
  - open `src/app/app.component.html` and add
  ```
  <div class="btn-group" dropdown>
  - <button id="single-button" type="button" class="btn btn-primary" dropdownToggle>
  + <button dropdownToggle type="button" class="btn btn-primary dropdown-toggle">
  Button dropdown <span class="caret"></span>
  </button>
  - <ul *dropdownMenu role="menu" aria-labelledby="single-button">
  + <ul *dropdownMenu class="dropdown-menu" role="menu">
  <li role="menuitem"><a class="dropdown-item" href="#">Action</a></li>
  <li role="menuitem"><a class="dropdown-item" href="#">Another action</a></li>
  <li role="menuitem"><a class="dropdown-item" href="#">Something else here</a></li>
  <li class="divider dropdown-divider"></li>
  - <li role="menuitem"><a class="dropdown-item" href="#">Separated link</a></li>
  + <li role="menuitem"><a class="dropdown-item" href="#">Separated link</a>
  + </li>
  </ul>
  </div>
  ```
  