[new feature] Toast support position prop (#244)

* [bugfix] Checkbox border render error in weixin browser

* [bugfix] TreeSelect dependency path error

* [bugfix] Swipe should clear autoplay timer when destroyed

* [bugfix] Optimize component dependency analyze when build style entry

* merge

* update yarn.lock

* update README.md

* update README.md

* update README.md

* update README.md

* update README.md

* [Doc] add more badges in README.md

* update README.md

* [bugfix] Address & Contact list style

* fix: contact test cases

* [bugfix] popup style missing when build style entry

* [bugfix] Search: onSearch event arguments missing

* [Doc] add demo pages

* update zan-doc@0.3.7

* fix: build entry error

* [Doc] add goods demo

* [bugfix] button primary background color

* [Doc] update doc detail

* [new feature] Coupon add 'showExchangeBar' prop && add empty style

* [new feature] Toast support `position` prop

* [new feature] Tabbar add 'info' prop

packages/toast/toast.vue

@@ -1,7 +1,7 @@
 <template>
   <transition name="van-toast-fade">
     <div class="van-toast-wrapper" v-show="visible">
-      <div :class="['van-toast', 'van-toast--' + displayStyle]">
+      <div :class="['van-toast', `van-toast--${displayStyle}`, `van-toast--${position}`]">
         <!-- text only -->
         <div v-if="displayStyle === 'text'" class="van-toast__text">{{ message }}</div>
         <div v-if="displayStyle === 'html'" class="van-toast__text" v-html="message" />
@@ -46,6 +46,10 @@ export default {
     forbidClick: {
       type: Boolean,
       default: false
+    },
+    position: {
+      type: String,
+      default: 'middle'
     }
   },