title: Button Clicking works when self-clicked, not automaitcally
body: <p>i'm new here. I try to work with greasemonkey to copy all whispers from a Path of Exile trade-search.</p>
  
  <p>It all works great when I click the meta-button I created myself. But whe I run the function via SetInterval it jest deletes the buttons, and doesn't click them before..</p>
  
  <p>What do I miss? I already tried a lot..</p>
  
  <pre><code>// ==UserScript==
  // @name         test
  // @namespace    https://nope
  // @version      0.0.0.1
  // @description  clicks whispers of poe-trade
  // @author       PJ
  // @license      no
  // @match        https://www.pathofexile.com/trade*
  // ==/UserScript==
  
  
  
  
  var input=document.createElement("input");
  input.type="button";
  input.value="Copy next";
  input.onclick = CopyWhisper;
  input.setAttribute("style", "font-size:18px;position:absolute;top:120px;right:40px;");
  document.body.appendChild(input);
  
  
  function CopyWhisper()
  {
      var allbuttons = document.getElementsByClassName("whisper-btn");
      var firstbutton = allbuttons[0];
      firstbutton.dispatchEvent(new MouseEvent('click'));
      firstbutton.remove();
  
  }
  
  setInterval(CopyWhisper, 5000);
  </code></pre>