vant-css: use hairline classes instead of mixins

packages/vant-css/src/toast.css

@@ -4,23 +4,26 @@
   position: fixed;
   z-index: 3001;
   border-radius: 5px;
-  background-color: #272727;
-  opacity: .7;
+  background-color: rgb(39, 39, 39, .7);
   top: 50%;
   left: 50%;
   transform: translate3d(-50%, -50%, 0);
   font-size: 12px;
-  color: $c-white;
+  color: $white;
   text-align: center;
   line-height: 12px;
 
+  &-wrapper {
+    transition: opacity .2s;
+  }
+
   &__overlay {
     position: fixed;
     left: 0;
     top: 0;
     background: transparent;
-    height: 100vh;
-    width: 100vh;
+    height: 100%;
+    width: 100%;
     z-index: 3000;
   }
 
@@ -28,7 +31,7 @@
     padding: 45px;
   }
 
-  &--text, html {
+  &--text {
     padding: 12px;
     min-width: 200px;
   }
@@ -50,9 +53,6 @@
   }
 }
 
-.van-toast-fade-enter-active, .van-toast-fade-leave-active {
-  transition: opacity .2s;
-}
 .van-toast-fade-enter, .van-toast-fade-leave-to {
   opacity: 0;
 }