feat(Stepper): improve disable-input behavior

src/stepper/demo/index.vue

@@ -20,6 +20,10 @@
       <van-stepper v-model="stepper5" disabled />
     </van-cell>
 
+    <van-cell center :title="$t('disableInput')">
+      <van-stepper v-model="disabledInput" disable-input />
+    </van-cell>
+
     <van-cell center :title="$t('decimalLength')">
       <van-stepper v-model="stepper8" :decimal-length="1" step="0.2" />
     </van-cell>
@@ -43,6 +47,7 @@ export default {
       integer: '限制输入整数',
       asyncChange: '异步变更',
       customSize: '自定义大小',
+      disableInput: '禁用输入框',
       decimalLength: '固定小数位数'
     },
     'en-US': {
@@ -51,6 +56,7 @@ export default {
       integer: 'Integer',
       asyncChange: 'Async Change',
       customSize: 'Custom Size',
+      disableInput: 'Disable Input',
       decimalLength: 'Decimal Length'
     }
   },
@@ -64,7 +70,8 @@ export default {
       stepper5: 1,
       stepper6: 1,
       stepper7: 1,
-      stepper8: 1
+      stepper8: 1,
+      disabledInput: 1
     };
   },