[new feature] Popup: add round prop (#3781)

src/popup/test/__snapshots__/demo.spec.js.snap

@@ -23,6 +23,11 @@ exports[`renders demo correctly 1`] = `
     </span></button>
     <!---->
   </div>
+  <div><button class="van-button van-button--primary van-button--normal"><span class="van-button__text">
+      圆角弹窗
+    </span></button>
+    <!---->
+  </div>
   <div><button class="van-button van-button--primary van-button--normal"><span class="van-button__text">
       指定挂载节点
     </span></button> </div>

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

@@ -3,3 +3,5 @@
 exports[`duration prop 1`] = `<div class="van-popup van-popup--center" style="transition-duration: 0.5s;" name="van-fade"></div>`;
 
 exports[`reset z-index 1`] = `<div class="van-popup van-popup--center" name="van-fade"></div>`;
+
+exports[`round prop 1`] = `<div class="van-popup van-popup--round van-popup--center" name="van-fade"></div>`;

src/popup/test/index.spec.js

@@ -211,3 +211,14 @@ test('duration prop', () => {
 
   expect(wrapper).toMatchSnapshot();
 });
+
+test('round prop', () => {
+  const wrapper = mount(Popup, {
+    propsData: {
+      value: true,
+      round: true
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});