feat(button): add new prop form-type (#3208)

fix #3204

packages/button/README.md

@@ -142,6 +142,7 @@
 | send-message-img | sendMessageImg | _string_ | 截图 | - |
 | show-message-card | 显示会话内消息卡片 | _string_ | `false` | - |
 | dataset | 按钮 dataset，open-type 为 `share` 时，可在 onShareAppMessage 事件的 `event.target.dataset.detail` 中看到传入的值 | _any_ | - | - |
+| form-type | 用于 form 组件，可选值为`submit` `reset`，点击分别会触发 form 组件的 submit/reset 事件 | _string_ | - | - |
 
 ### Events
 

packages/button/index.ts

@@ -3,7 +3,7 @@ import { button } from '../mixins/button';
 import { openType } from '../mixins/open-type';
 
 VantComponent({
-  mixins: [button, openType],
+  mixins: [button, openType, 'wx://form-field-button'],
 
   classes: ['hover-class', 'loading-class'],
 
@@ -12,6 +12,7 @@ VantComponent({
   },
 
   props: {
+    formType: String,
     icon: String,
     classPrefix: {
       type: String,

packages/button/index.wxml

@@ -6,6 +6,7 @@
   class="custom-class {{ utils.bem('button', [type, size, { block, round, plain, square, loading, disabled, hairline, unclickable: disabled || loading }]) }} {{ hairline ? 'van-hairline--surround' : '' }}"
   hover-class="van-button--active hover-class"
   lang="{{ lang }}"
+  form-type="{{ formType }}"
   style="{{ baseStyle }} {{ customStyle }}"
   open-type="{{ disabled ? '' : openType }}"
   business-id="{{ businessId }}"