feat(Dialog): add footer slot (#8382)

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

@@ -29,6 +29,20 @@ exports[`should render default slot correctly 1`] = `
 </div>
 `;
 
+exports[`should render footer slot correctly 1`] = `
+<div class="van-popup van-popup--center van-dialog"
+     role="dialog"
+     aria-labelledby="message"
+>
+  <div class="van-dialog__content van-dialog__content--isolated">
+    <div class="van-dialog__message">
+      message
+    </div>
+  </div>
+  Custom Footer
+</div>
+`;
+
 exports[`should render title slot correctly 1`] = `
 <div class="van-dialog__header van-dialog__header--isolated">
   Custom Title

src/dialog/test/index.spec.js

@@ -129,3 +129,16 @@ test('should update width when using width prop', async () => {
   const dialog = wrapper.find('.van-dialog').element;
   expect(dialog.style.width).toEqual('200px');
 });
+
+test('should render footer slot correctly', () => {
+  const wrapper = mount(Dialog, {
+    props: {
+      show: true,
+      message: 'message',
+    },
+    slots: {
+      footer: () => 'Custom Footer',
+    },
+  });
+  expect(wrapper.find('.van-dialog').html()).toMatchSnapshot();
+});