style(Field): adjust field placeholder color to gray-5 (#6304)

src/field/README.md

@@ -17,7 +17,7 @@ The value of field is bound with v-model.
 
 ```html
 <van-cell-group>
-  <van-field v-model="value" placeholder="Text" />
+  <van-field v-model="value" label="Label" placeholder="Text" />
 </van-cell-group>
 ```
 

src/field/README.zh-CN.md

@@ -22,7 +22,7 @@ Vue.use(Field);
 ```html
 <!-- Field 是基于 Cell 实现的，可以使用 CellGroup 作为容器来提供外边框。 -->
 <van-cell-group>
-  <van-field v-model="value" placeholder="请输入用户名" />
+  <van-field v-model="value" label="文本" placeholder="请输入用户名" />
 </van-cell-group>
 ```
 

src/field/demo/BasicUsage.vue

@@ -1,7 +1,11 @@
 <template>
   <demo-block :title="t('basicUsage')">
     <van-cell-group>
-      <van-field v-model="value" :placeholder="t('placeholder')" />
+      <van-field
+        v-model="value"
+        :label="t('label')"
+        :placeholder="t('placeholder')"
+      />
     </van-cell-group>
   </demo-block>
 </template>
@@ -10,9 +14,11 @@
 export default {
   i18n: {
     'zh-CN': {
+      label: '文本',
       placeholder: '请输入文本',
     },
     'en-US': {
+      label: 'Label',
       placeholder: 'Text',
     },
   },

src/field/test/__snapshots__/demo.spec.js.snap

@@ -5,7 +5,8 @@ exports[`renders demo correctly 1`] = `
   <div>
     <div class="van-cell-group van-hairline--top-bottom">
       <div class="van-cell van-field">
-        <div class="van-cell__value van-cell__value--alone van-field__value">
+        <div class="van-cell__title van-field__label"><span>文本</span></div>
+        <div class="van-cell__value van-field__value">
           <div class="van-field__body"><input type="text" placeholder="请输入文本" class="van-field__control"></div>
         </div>
       </div>

src/style/var.less

@@ -349,7 +349,7 @@
 @field-input-text-color: @text-color;
 @field-input-error-text-color: @red;
 @field-input-disabled-text-color: @gray-6;
-@field-placeholder-text-color: @gray-6;
+@field-placeholder-text-color: @gray-5;
 @field-icon-size: 16px;
 @field-clear-icon-size: 16px;
 @field-clear-icon-color: @gray-5;