update copy code

source/less/_header.less

@@ -285,7 +285,42 @@
   }
 }
 
-
+//代码块复制按钮
+.highlight{
+    //方便copy代码按钮（btn-copy）的定位
+    position: relative;
+}
+.btn-copy {
+    display: inline-block;
+    cursor: pointer;
+    background-color: #eee;
+    background-image: linear-gradient(#fcfcfc,#eee);
+    border: 1px solid #d5d5d5;
+    border-radius: 3px;
+    -webkit-user-select: none;
+    -moz-user-select: none;
+    -ms-user-select: none;
+    user-select: none;
+    -webkit-appearance: none;
+    font-size: 13px;
+    font-weight: 700;
+    line-height: 20px;
+    color: #333;
+    -webkit-transition: opacity .3s ease-in-out;
+    -o-transition: opacity .3s ease-in-out;
+    transition: opacity .3s ease-in-out;
+    padding: 2px 6px;
+    position: absolute;
+    right: 5px;
+    top: 5px;
+    opacity: 0;
+}
+.btn-copy span {
+    margin-left: 5px;
+}
+.highlight:hover .btn-copy{
+    opacity: 1;
+}
 
 .menu-phone{
   .header{