title: how to make widgets in jupyter notebook scrollable?
body: <p>For some reason, I want to my HTML widget to have fixed height, no matter how many lines there are in the widget. If the lines are too many to fit into the height, ideally one can scroll to see all the lines. I tried something like the following, but it does not work:</p>
  
  <pre><code>import ipywidgets as widgets
  widgets.HTML(
      value="Hello &lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;&lt;p&gt;World&lt;/p&gt;",
      placeholder='Some HTML',
      description='Some HTML',
      disabled=True,
      height='50px',
      overflow_y='scroll'
  )
  </code></pre>