[new feature] add IndexBar component

packages/index-anchor/index.js

@@ -0,0 +1,26 @@
+import { use } from '../utils';
+import { ChildrenMixin } from '../mixins/relation';
+
+const [sfc, bem] = use('index-anchor');
+
+export default sfc({
+  mixins: [ChildrenMixin('vanIndexBar', { indexKey: 'childrenIndex' })],
+
+  props: {
+    index: [String, Number]
+  },
+
+  methods: {
+    scrollIntoView() {
+      this.$el.scrollIntoView();
+    }
+  },
+
+  render(h) {
+    return (
+      <div class={bem()}>
+        {this.slots('default') ? this.slots('default') : this.index}
+      </div>
+    );
+  }
+});

packages/index-anchor/index.less

@@ -0,0 +1,8 @@
+@import '../style/var';
+
+.van-index-anchor {
+  padding: 0 15px;
+  font-size: 14px;
+  font-weight: 500;
+  line-height: 32px;
+}