Fixed transparency of background items

examples/timeline/25_background_areas.html

@@ -12,9 +12,6 @@
     .vis-item.vis-background.negative {
       background-color: rgba(255, 0, 0, 0.2);
     }
-    .vis-item.vis-background.marker {
-      border-left: 2px solid green;
-    }
   </style>
 
   <script src="../../dist/vis.js"></script>

lib/timeline/component/css/item.css

@@ -49,7 +49,7 @@
   box-sizing: border-box;
 }
 
-.vis-item.background {
+.vis-item.vis-background {
   border: none;
   background-color: rgba(213, 221, 246, 0.4);
   box-sizing: border-box;
@@ -71,7 +71,7 @@
   display: inline-block;
 }
 
-.vis-item.background .vis-item-content {
+.vis-item.vis-background .vis-item-content {
   position: absolute;
   display: inline-block;
 }