[new feature] NumberKeyboard: add title-left slot (#3194)

packages/number-keyboard/test/__snapshots__/demo.spec.js.snap

@@ -6,7 +6,7 @@ exports[`renders demo correctly 1`] = `
       弹出默认键盘
     </span></button>
     <div name="van-slide-up" class="van-number-keyboard van-number-keyboard--default" style="z-index:100;">
-      <div class="van-number-keyboard__title van-hairline--top"><span></span><span class="van-number-keyboard__close">完成</span></div>
+      <div class="van-number-keyboard__title van-hairline--top"><span class="van-number-keyboard__close">完成</span></div>
       <div class="van-number-keyboard__body"><i class="van-hairline van-key">1</i><i class="van-hairline van-key">2</i><i class="van-hairline van-key">3</i><i class="van-hairline van-key">4</i><i class="van-hairline van-key">5</i><i class="van-hairline van-key">6</i><i class="van-hairline van-key">7</i><i class="van-hairline van-key">8</i><i class="van-hairline van-key">9</i><i class="van-hairline van-key van-key--gray">.</i><i class="van-hairline van-key">0</i><i class="van-hairline van-key van-key--gray van-key--delete">删除</i></div>
     </div>
   </div>

packages/number-keyboard/test/__snapshots__/index.spec.js.snap

@@ -0,0 +1,8 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`title-left slot 1`] = `
+<div class="van-number-keyboard van-number-keyboard--default" style="z-index: 100;" name="van-slide-up">
+  <div class="van-number-keyboard__title van-hairline--top"><span class="van-number-keyboard__title-left">Custom Title Left</span></div>
+  <div class="van-number-keyboard__body"><i class="van-hairline van-key">1</i><i class="van-hairline van-key">2</i><i class="van-hairline van-key">3</i><i class="van-hairline van-key">4</i><i class="van-hairline van-key">5</i><i class="van-hairline van-key">6</i><i class="van-hairline van-key">7</i><i class="van-hairline van-key">8</i><i class="van-hairline van-key">9</i><i class="van-hairline van-key van-key--gray"></i><i class="van-hairline van-key">0</i><i class="van-hairline van-key van-key--gray van-key--delete">删除</i></div>
+</div>
+`;

packages/number-keyboard/test/index.spec.js

@@ -83,3 +83,19 @@ test('listen to show event when no transtion', () => {
   expect(wrapper.emitted('show')).toBeTruthy();
   expect(wrapper.emitted('hide')).toBeTruthy();
 });
+
+test('title-left slot', () => {
+  const wrapper = mount({
+    template: `
+      <number-keyboard show>
+        <template v-slot:title-left>Custom Title Left</template>
+      </number-keyboard>
+    `
+  }, {
+    components: {
+      NumberKeyboard
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});