title: How to get last unchecked item in ngx-treeview?
body: <p>I am using npm module named as <a href="https://www.npmjs.com/package/ngx-treeview" rel="nofollow noreferrer"><code>ngx-treeview</code></a>  . In this I can get the all selected items on change but not that one specific item which is getting changed. I am looking for uncheck.</p>
  
  <p>In component.html file:</p>
  
  <pre><code>&lt;ngx-treeview [config]="treeviewConfig" [items]="treeItems" [itemTemplate]="itemTemplate" (selectedChange)="onSelectedChange($event,$event)"&gt;&lt;/ngx-treeview&gt;
  </code></pre>
  
  <p>In component.ts file:
  First I have imported the ngx-treeview as </p>
  
  <pre><code>import { TreeviewItem, TreeviewConfig, TreeviewHelper, TreeviewComponent, TreeviewEventParser, OrderDownlineTreeviewEventParser, DownlineTreeviewItem } from 'ngx-treeview/src';
  
  
  // function to be called
  public onSelectedChange(downlineItems: DownlineTreeviewItem[], item: TreeviewItem ) {
     console.log(downlineItems);
  
     console.log(item);
  }
  </code></pre>
  
  <p>Can anyone please let me know how can I get just unchecked item's value?</p>