feat(Icon): add dot prop (#4425)

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

@@ -1,5 +1,11 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`dot prop 1`] = `
+<i class="van-icon van-icon-undefined">
+  <div class="van-info van-info--dot"></div>
+</i>
+`;
+
 exports[`render icon default slot 1`] = `
 <i class="van-icon van-icon-success">Default slot
   <!----></i>

src/icon/test/index.spec.js

@@ -46,6 +46,15 @@ test('tag prop', () => {
   expect(wrapper).toMatchSnapshot();
 });
 
+test('dot prop', () => {
+  const wrapper = mount(Icon, {
+    propsData: {
+      dot: true
+    }
+  });
+  expect(wrapper).toMatchSnapshot();
+});
+
 test('size without unit', () => {
   const wrapper = mount(Icon, {
     propsData: {