title: sub menu when onClick in React
body: <p>hello guys i am new to react and trying to go through and finish this project, i need help with sub-menu. what i have is a toolbar created and has a square icon and what i want is when i press on this icon a sub-menu like this pop-up below it:</p>
  
  <p>so far i wrote the toolbar and added the icon like this:</p>
  
  <pre><code>const toolbar = (props) =&gt; (
      &lt;header&gt;
          &lt;ul className="Toolbar"&gt;
              &lt;ul className="align-items"&gt;
              &lt;li className="closer-to-sidebar"&gt;&lt;img src = {square} alt="square icon"/&gt;&lt;/li&gt;
              &lt;/ul&gt;
          &lt;/ul&gt;
      &lt;/header&gt;
  );
  </code></pre>
  
  <p>i just have a problem to do this and couldn't find any relevant solution any help would be much appreciated thank you </p>