[new feature] Slider: add button slot (#2373)

packages/slider/demo/index.vue

@@ -27,10 +27,28 @@
       <van-slider
         v-model="value4"
         :step="10"
+        @change="onChange"
+      />
+    </demo-block>
+
+    <demo-block :title="$t('customStyle')">
+      <van-slider
+        v-model="value5"
         bar-height="4px"
         @change="onChange"
       />
     </demo-block>
+
+    <demo-block :title="$t('customButton')">
+      <van-slider v-model="value6">
+        <div
+          slot="button"
+          class="custom-button"
+        >
+          {{ value6 }}
+        </div>
+      </van-slider>
+    </demo-block>
   </demo-section>
 </template>
 
@@ -42,6 +60,8 @@ export default {
       title2: '指定选择范围',
       title3: '禁用',
       title4: '指定步长',
+      customStyle: '自定义样式',
+      customButton: '自定义按钮',
       text: '当前值：'
     },
     'en-US': {
@@ -49,6 +69,8 @@ export default {
       title2: 'Range',
       title3: 'Disabled',
       title4: 'Step size',
+      customStyle: 'Custom Style',
+      customButton: 'Custom Button',
       text: 'Current value: '
     }
   },
@@ -58,7 +80,9 @@ export default {
       value1: 50,
       value2: 50,
       value3: 50,
-      value4: 50
+      value4: 50,
+      value5: 50,
+      value6: 50
     };
   },
 
@@ -71,11 +95,27 @@ export default {
 </script>
 
 <style lang="less">
+@import '../../style/var';
+
 .demo-slider {
   user-select: none;
 
   .van-slider {
     margin: 0 15px 30px;
   }
+
+  .custom-button {
+    width: 26px;
+    color: #fff;
+    font-size: 10px;
+    line-height: 18px;
+    text-align: center;
+    border-radius: 100px;
+    background-color: @red;
+  }
+
+  .van-doc-demo-block__title {
+    padding-top: 25px;
+  }
 }
 </style>