feat(Picker): item-height support rem unit (#6462)

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

@@ -103,6 +103,27 @@ exports[`render title slot 1`] = `
 </div>
 `;
 
+exports[`set rem item-height 1`] = `
+<div class="van-picker">
+  <!---->
+  <div class="van-picker__columns" style="height: 800px;">
+    <div class="van-picker-column">
+      <ul class="van-picker-column__wrapper" style="transform: translate3d(0, 320px, 0); transition-duration: 0ms; transition-property: none;">
+        <li role="button" tabindex="0" class="van-picker-column__item van-picker-column__item--selected" style="height: 160px;">
+          <div class="van-ellipsis">1990</div>
+        </li>
+        <li role="button" tabindex="0" class="van-picker-column__item" style="height: 160px;">
+          <div class="van-ellipsis">1991</div>
+        </li>
+      </ul>
+    </div>
+    <div class="van-picker__mask" style="background-size: 100% 320px;"></div>
+    <div class="van-hairline-unset--top-bottom van-picker__frame" style="height: 160px;"></div>
+  </div>
+  <!---->
+</div>
+`;
+
 exports[`toolbar-position prop 1`] = `
 <div class="van-picker">
   <!---->

src/picker/test/index.spec.js

@@ -261,3 +261,21 @@ test('should not reset index when columns unchanged', () => {
   wrapper.find('.van-picker__confirm').trigger('click');
   expect(wrapper.emitted('confirm')[0]).toEqual(['2', 1]);
 });
+
+test('set rem item-height', async () => {
+  const originGetComputedStyle = window.getComputedStyle;
+
+  window.getComputedStyle = () => ({ fontSize: '16px' });
+
+  const wrapper = mount(Picker, {
+    propsData: {
+      columns: simpleColumn.slice(0, 2),
+      itemHeight: '10rem',
+    },
+  });
+
+  await later();
+  expect(wrapper).toMatchSnapshot();
+
+  window.getComputedStyle = originGetComputedStyle;
+});