feat(Tabs): add nav-bottom slot (#8915)

src/tab/test/__snapshots__/insert.spec.tsx.snap

@@ -160,3 +160,19 @@ exports[`should render correctly after inserting a tab with name 1`] = `
   </div>
 </div>
 `;
+
+exports[`should render nav-bottom slot correctly 1`] = `
+<div class="van-tabs van-tabs--line">
+  <div class="van-tabs__wrap">
+    <div role="tablist"
+         class="van-tabs__nav van-tabs__nav--line"
+    >
+      <div class="van-tabs__line">
+      </div>
+    </div>
+  </div>
+  Nav Bottom
+  <div class="van-tabs__content">
+  </div>
+</div>
+`;

src/tab/test/insert.spec.tsx

@@ -86,3 +86,14 @@ test('should render Tab inside a component correctly', async () => {
   await later();
   expect(wrapper.html()).toMatchSnapshot();
 });
+
+test('should render nav-bottom slot correctly', async () => {
+  const wrapper = mount(Tabs, {
+    slots: {
+      'nav-bottom': () => 'Nav Bottom',
+    },
+  });
+
+  await later();
+  expect(wrapper.html()).toMatchSnapshot();
+});