docs(PullRefresh): add custom tip demo

src/pull-refresh/test/__snapshots__/demo.spec.js.snap

@@ -6,7 +6,8 @@ exports[`renders demo correctly 1`] = `
     <div class="van-tabs__wrap van-hairline--top-bottom">
       <div role="tablist" class="van-tabs__nav van-tabs__nav--line">
         <div role="tab" aria-selected="true" class="van-tab van-tab--active van-ellipsis"><span class="van-tab__text">基础用法<!----></span></div>
-        <div role="tab" class="van-tab van-ellipsis"><span class="van-tab__text">刷新成功提示<!----></span></div>
+        <div role="tab" class="van-tab van-ellipsis"><span class="van-tab__text">成功提示<!----></span></div>
+        <div role="tab" class="van-tab van-ellipsis"><span class="van-tab__text">自定义提示<!----></span></div>
         <div class="van-tabs__line" style="width: 0px; transform: translateX(0px) translateX(-50%);"></div>
       </div>
     </div>
@@ -22,6 +23,9 @@ exports[`renders demo correctly 1`] = `
       <div role="tabpanel" class="van-tab__pane" style="display: none;">
         <!---->
       </div>
+      <div role="tabpanel" class="van-tab__pane" style="display: none;">
+        <!---->
+      </div>
     </div>
   </div>
 </div>

src/pull-refresh/test/__snapshots__/index.spec.js.snap

@@ -105,3 +105,11 @@ exports[`render success text 2`] = `
   </div>
 </div>
 `;
+
+exports[`should set height when using head-height 1`] = `
+<div class="van-pull-refresh">
+  <div class="van-pull-refresh__track" style="transition-duration: 0ms;">
+    <div class="van-pull-refresh__head" style="height: 100px;"></div>
+  </div>
+</div>
+`;

src/pull-refresh/test/index.spec.js

@@ -156,3 +156,13 @@ test('render success slot', async () => {
   wrapper.setProps({ value: false });
   expect(wrapper).toMatchSnapshot();
 });
+
+test('should set height when using head-height', async () => {
+  const wrapper = mount(PullRefresh, {
+    propsData: {
+      headHeight: 100
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});