feat: add transition animation

packages/toast/src/toast.vue

@@ -1,5 +1,5 @@
 <template>
-  <transition name="zan-toast">
+  <transition name="zan-toast-fade">
     <div class="zan-toast-wrapper" v-show="visible">
       <div class="zan-toast" :class="['zan-toast--' + displayStyle]">
         <!-- 只显示文字 -->

packages/zanui-css/src/toast.css

@@ -50,3 +50,7 @@
     }
   }
 }
+
+.zan-toast-fade-enter, .zan-toast-fade-leave-active {
+  opacity: 0;
+}