[bugfix] Icon: info z-index higher than image

fix #1393

packages/icon/index.less

@@ -7,14 +7,18 @@
     height: 1em;
 
     image {
+      position: absolute;
       top: 0;
-      left: 0;
       right: 0;
       bottom: 0;
-      margin: auto;
+      left: 0;
       max-width: 100%;
       max-height: 100%;
-      position: absolute;
+      margin: auto;
     }
   }
+
+  &__info {
+    z-index: 1;
+  }
 }

packages/icon/index.wxml

@@ -8,6 +8,7 @@
   <van-info
     wx:if="{{ info !== null }}"
     info="{{ info }}"
+    custom-class="van-icon__info"
   />
   <image
     wx:if="{{ utils.isSrc(name) }}"