title: Prevent dropdown from closing in ComposeView inboxSDK
body: <p>I am injecting an icon in compose's toolbar with hasDropdown marked as true. But when the dropdown is visible and if I click on the toolbar's button or if I click outside the dropdown, the dropdown disappers. I want to prevent this default behaviour. Although dropdown object is passed under event inside onClick, but I am unable to attach any listeners to it.</p>
  <p>Code through which I am injecting button</p>
  <pre><code>    InboxSDK.load(2, &quot;&lt;key&gt;&quot;).then(function (sdk) {
      sdk.Compose.registerComposeViewHandler(function (composeView) {
        // a compose view has come into existence, do something with it!
        composeView.addButton({
          title: &quot;Title of the icon&quot;,
          iconUrl: &quot;url of the icon&quot;,
          hasDropdown: true,
          onClick: function (event) {
            //prevent dropdown from closing if the  dropdown is already visible
          },
        });
      });
    });
  </code></pre>