feat(Area): add columns-top、columns-bottom prop (#5719)

src/area/test/__snapshots__/index.spec.js.snap

@@ -114,6 +114,26 @@ exports[`columns-num prop 1`] = `
 </div>
 `;
 
+exports[`columns-top、columns-bottom slot 1`] = `
+<div class="van-picker van-area">
+  <div class="van-hairline--top-bottom van-picker__toolbar"><button type="button" class="van-picker__cancel">取消</button><button type="button" class="van-picker__confirm">确认</button></div>
+  <!---->Top<div class="van-picker__columns" style="height: 220px;">
+    <div class="van-picker-column">
+      <ul class="van-picker-column__wrapper" style="transform: translate3d(0, 88px, 0); transition-duration: 0ms; transition-property: none; line-height: 44px;"></ul>
+    </div>
+    <div class="van-picker-column">
+      <ul class="van-picker-column__wrapper" style="transform: translate3d(0, 88px, 0); transition-duration: 0ms; transition-property: none; line-height: 44px;"></ul>
+    </div>
+    <div class="van-picker-column">
+      <ul class="van-picker-column__wrapper" style="transform: translate3d(0, 88px, 0); transition-duration: 0ms; transition-property: none; line-height: 44px;"></ul>
+    </div>
+    <div class="van-picker__mask" style="background-size: 100% 88px;"></div>
+    <div class="van-hairline-unset--top-bottom van-picker__frame" style="height: 44px;"></div>
+  </div>Bottom
+  <!---->
+</div>
+`;
+
 exports[`reset method 1`] = `
 <div class="van-picker van-area">
   <div class="van-hairline--top-bottom van-picker__toolbar"><button type="button" class="van-picker__cancel">取消</button><button type="button" class="van-picker__confirm">确认</button></div>

src/area/test/index.spec.js

@@ -139,3 +139,15 @@ test('title slot', async () => {
   await later();
   expect(wrapper).toMatchSnapshot();
 });
+
+test('columns-top、columns-bottom slot', async () => {
+  const wrapper = mount(Area, {
+    slots: {
+      'columns-top': 'Top',
+      'columns-bottom': 'Bottom',
+    },
+  });
+
+  await later();
+  expect(wrapper).toMatchSnapshot();
+});