[new feature] NoticeBar: add right-icon prop

packages/notice-bar/test/__snapshots__/index.spec.js.snap

@@ -1,10 +1,9 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`left-icon slot 1`] = `
+exports[`icon slot 1`] = `
 <div class="van-notice-bar">Custom Left Icon<div class="van-notice-bar__wrap">
     <div class="van-notice-bar__content" style="padding-left: 0px; animation-delay: 1s; animation-duration: 0s;">
       Content
     </div>
-  </div>
-</div>
+  </div>Custom Right Icon</div>
 `;

packages/notice-bar/test/index.spec.js

@@ -13,12 +13,13 @@ test('close event', () => {
   expect(wrapper.emitted('close')).toBeTruthy();
 });
 
-test('left-icon slot', () => {
+test('icon slot', () => {
   const wrapper = mount({
     template: `
       <notice-bar>
         Content
         <template v-slot:left-icon>Custom Left Icon</template>
+        <template v-slot:right-icon>Custom Right Icon</template>
       </notice-bar>
     `,
     components: {