[Improvement] Tab: add title slot (#603)

docs/demos/views/tab.vue

@@ -47,6 +47,17 @@
         </van-tab>
       </van-tabs>
     </demo-block>
+
+    <demo-block :title="$t('title7')">
+      <van-tabs :active="active">
+        <van-tab v-for="index in 2" :key="index">
+          <div slot="title">
+            <van-icon name="more-o" />{{ $t('tab') }}
+          </div>
+          {{ $t('content') }} {{ index }}
+        </van-tab>
+      </van-tabs>
+    </demo-block>
   </demo-section>
 </template>
 
@@ -59,7 +70,8 @@ export default {
       title3: '禁用标签',
       title4: '样式风格',
       title5: '点击事件',
-      title6: '粘性布局'
+      title6: '粘性布局',
+      title7: '自定义标签'
     },
     'en-US': {
       tab: 'Tab ',
@@ -68,7 +80,8 @@ export default {
       title3: 'Disabled Tab',
       title4: 'Card Style',
       title5: 'Click Event',
-      title6: 'Sticky'
+      title6: 'Sticky',
+      title7: 'Custom Tab'
     }
   },
 
@@ -79,12 +92,6 @@ export default {
     };
   },
 
-  mounted() {
-    setTimeout(() => {
-      this.active = 3;
-    }, 1000);
-  },
-
   methods: {
     onClickDisabled() {
       Toast('Disabled!');
@@ -101,6 +108,11 @@ export default {
 .demo-tab {
   margin-bottom: 700px;
 
+  .van-tab .van-icon {
+    margin-right: 5px;
+    vertical-align: -2px;
+  }
+
   .van-tab__pane {
     background-color: #fff;
     padding: 20px;