[improvement] Toast: text align center when multi line

packages/toast/index.less

@@ -5,6 +5,7 @@
   top: 50%;
   left: 50%;
   display: flex;
+  text-align: center;
   color: @toast-text-color;
   max-width: @toast-max-width;
   font-size: @toast-font-size;