feat(Calendar): add subtitle slot (#8980)

src/calendar/test/__snapshots__/index.spec.ts.snap

@@ -900,28 +900,14 @@ exports[`row-height prop 1`] = `
 </div>
 `;
 
-exports[`should render top-info and bottom-info slot correctly 1`] = `
-<div role="gridcell"
-     style="margin-left: 71.42857142857143%;"
-     class="van-calendar__day van-calendar__day--disabled"
->
-  <div class="van-calendar__top-info">
-    top: 1
-  </div>
-  1
-  <div class="van-calendar__bottom-info">
-    bottom: 1
-  </div>
-</div>
-`;
-
-exports[`title & footer slot 1`] = `
+exports[`should render title、footer、subtitle slot correctly 1`] = `
 <div class="van-calendar">
   <div class="van-calendar__header">
     <div class="van-calendar__header-title">
       Custom Title
     </div>
     <div class="van-calendar__header-subtitle">
+      Custom Subtitle
     </div>
     <div class="van-calendar__weekdays">
       <span class="van-calendar__weekday">
@@ -1132,3 +1118,18 @@ exports[`title & footer slot 1`] = `
   </div>
 </div>
 `;
+
+exports[`should render top-info and bottom-info slot correctly 1`] = `
+<div role="gridcell"
+     style="margin-left: 71.42857142857143%;"
+     class="van-calendar__day van-calendar__day--disabled"
+>
+  <div class="van-calendar__top-info">
+    top: 1
+  </div>
+  1
+  <div class="van-calendar__bottom-info">
+    bottom: 1
+  </div>
+</div>
+`;

src/calendar/test/index.spec.ts

@@ -344,7 +344,7 @@ test('formatter prop', async () => {
   expect(wrapper.html()).toMatchSnapshot();
 });
 
-test('title & footer slot', async () => {
+test('should render title、footer、subtitle slot correctly', async () => {
   const wrapper = mount(Calendar, {
     props: {
       minDate,
@@ -356,6 +356,7 @@ test('title & footer slot', async () => {
     slots: {
       title: () => 'Custom Title',
       footer: () => 'Custom Footer',
+      subtitle: () => 'Custom Subtitle',
     },
   });