add Select Component

add Select Component

components/select/option-group.vue

@@ -0,0 +1,25 @@
+<template>
+    <li :class="[`${prefixCls}-wrap`]">
+        <div :class="[`${prefixCls}-title`]">{{ label }}</div>
+        <ul>
+            <li :class="[`${prefixCls}`]"><slot></slot></li>
+        </ul>
+    </li>
+</template>
+<script>
+    const prefixCls = 'ivu-select-group';
+
+    export default {
+        props: {
+            label: {
+                type: String,
+                default: ''
+            }
+        },
+        data () {
+            return {
+                prefixCls: prefixCls
+            }
+        }
+    }
+</script>