[breaking change] Cell: show active color when clicked (#497)

packages/vant-css/src/cell.css

@@ -3,20 +3,21 @@
 .van-cell {
   width: 100%;
   display: table;
-  padding: 10px 15px 10px 0;
+  padding: 10px 15px;
   box-sizing: border-box;
   line-height: 24px;
+  position: relative;
   background-color: $white;
   color: $text-color;
   font-size: 14px;
   overflow: hidden;
 
   &:not(:last-child)::after {
+    left: 15px;
     border-bottom-width: 1px;
   }
 
   &-group {
-    padding-left: 15px;
     background-color: $white;
   }
 
@@ -47,12 +48,18 @@
     vertical-align: middle;
     overflow: hidden;
 
+    &--alone {
+      text-align: left;
+    }
+
     &--link {
       padding-right: 20px;
     }
+  }
 
-    &--alone {
-      text-align: left;
+  &--clickable {
+    &:active {
+      background-color: $active-color;
     }
   }