feat(docs) improvements to examples

* examples are now loaded only when they are visible on your screen
* stylistic improvements
* support for a description

docs/_static/css/custom.css

@@ -19,7 +19,7 @@ span.pre:first-child
 
 code.sig-name
 {
-  //margin-left:8px;
+  /*margin-left:8px;*/
 }
 
 .toggle .header {
@@ -64,11 +64,42 @@ code.sig-name
   transform: translate(0, -10px);
 }
 
-.lv-example {
+.lv-example, .lv-example > iframe {
   border: none;
   outline: none;
   padding: none;
   display: block;
   width: 320px;
   height: 240px;
+  flex: none;
+  position: relative;
 }
+.lv-example > iframe {
+  position: absolute;
+  top: 0;
+  left: 0;
+}
+
+.lv-example-container {
+    display: flex;
+}
+.lv-example-description {
+    flex: 1 1 auto;
+}
+
+.lv-example-link-button {
+    display: inline-block;
+    padding: 4px 8px;
+    border-radius: 4px;
+    background-color: #2980b9;
+    color: white;
+    margin: 0 4px;
+}
+.lv-example-link-button:hover {
+    color: white;
+    filter: brightness(120%);
+}
+
+.lv-example-link-button:visited {
+    color: white;
+}