title: Check if it is webview or browser
body: <p>Hi i want to detect if website is opened on webview or in a browser. The php code which works is: </p>
  
  <pre><code>&lt;?php if (isset($_SERVER['HTTP_X_REQUESTED_WITH']) == "com.website.reader") { ?&gt; 
  &lt;p&gt; it works &lt;/p&gt; 
  &lt;?php } ?&gt;
  </code></pre>
  
  <p>I want to check also it with javascript but when i tried to check it by getting headers like that: </p>
  
  <pre><code>    var headerAppend = document.querySelector(".headers-append");
  
      var req = new XMLHttpRequest();
      req.open('GET', "com.woblink.reader", false);
      req.send(null);
      var headers = req.getAllResponseHeaders();
  </code></pre>
  
  <p>I got only "client via: shouldInterceptRequest content-length: 2582 content-tpe: text/html"</p>
  
  <p>How to achieve it also in JS? User agent doesn't work.</p>