title: How to add scroll bar for React bootstrap DropDown?
body: <p>I am using react bootstrap dropdown, <a href="https://react-bootstrap.github.io/components/dropdowns/" rel="nofollow noreferrer">from here</a></p>
  
  <p>When the items in my drop down list are many, the list gets overflown vertically which is not responsive as shown in the snapshot <a href="https://i.stack.imgur.com/PACrq.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PACrq.jpg" alt="enter image description here"></a>
  I want to add a scroll bar to it but am not able to. Please help.</p>
  
  <p>This is my sample code</p>
  
  <pre><code>            &lt;DropdownButton
                  id="dropdown-basic-button"
                  title={this.props.passenger.seatNumber}
                  onSelect={(evt) =&gt; this.handleSeatSelection(evt)}
                  variant="info"
                &gt;
                  {this.state.availableSeatNumbers.map((seatNumber) =&gt; (
                    &lt;Dropdown.Item key={seatNumber} eventKey={seatNumber}&gt;
                      {seatNumber}
                    &lt;/Dropdown.Item&gt;
                  ))}
                &lt;/DropdownButton&gt;
  </code></pre>