Add screenshot on index page

Author: jackycute

public/css/cover.css

@@ -354,6 +354,12 @@ input {
     color: white;
 }
 
+.screenshot {
+    margin: 30px auto;
+    width: 100%;
+    border-radius: 3px;
+}
+
 select {
     color: black;
 }

public/screenshot.png

@@ -87,6 +87,7 @@
                             <a type="button" href="<%- url %>/features" class="btn btn-lg btn-primary" style="min-width: 200px;"><%= __('Explore all features') %></a>
                             <br>
                             <br>
+                            <img src="<%- url %>/screenshot.png" class="screenshot ui-signin">
                         </span>
                         <div class="lead row" style="width: 90%; margin: 0 auto;">
                             <div class="col-md-4 inner">