docs(index): fix screenshot

Author: trollixx

index.html

@@ -5,7 +5,7 @@
 <main class="zd-hp-header" id="content" tabindex="-1">
   <div class="container">
     <p class="lead">Zeal is an offline documentation browser for software developers.</p>
-    <img src="https://i.imgur.com/VmIoOF1.png" class="img-responsive center-block" alt="Screenshot of Zeal">
+    <img src="https://i.imgur.com/lWso18u.png" class="img-responsive center-block" alt="Screenshot of Zeal">
     <p class="lead">
       <a href="/download.html#windows" class="btn btn-primary btn-outline"><i class="fa fa-windows fa-lg"></i> Download for Windows</a>
       <a href="/download.html#linux" class="btn btn-danger btn-outline"><i class="fa fa-linux fa-lg"></i> Download for Linux</a>