[Improvement] Field: support clearable (#1309)

packages/coupon-list/index.vue

@@ -2,9 +2,10 @@
   <div :class="b()">
     <cell-group v-if="showExchangeBar" :class="b('top')">
       <field
+        v-model="currentCode"
+        clearable
         :class="b('field')"
         class="van-hairline--surround"
-        v-model="currentCode"
         :placeholder="inputPlaceholder || $t('placeholder')"
         :maxlength="20"
       />

packages/coupon-list/test/__snapshots__/demo.spec.js.snap

@@ -22,9 +22,12 @@ exports[`renders demo correctly 1`] = `
             <!---->
             <!---->
             <div class="van-cell__value van-cell__value--alone">
-              <input type="text" placeholder="请输入优惠码" maxlength="20" value="" class="van-field__control">
-              <!---->
-              <!---->
+              <div class="van-field__body">
+                <input type="text" placeholder="请输入优惠码" maxlength="20" value="" class="van-field__control">
+                <!---->
+                <!---->
+                <!---->
+              </div>
               <!---->
             </div>
             <!---->