feature: add drag select component (#1249)

src/views/components-demo/dragSelect.vue

@@ -0,0 +1,43 @@
+<template>
+  <div class="components-container">
+
+    <el-drag-select v-model="value" style="width:500px;" multiple placeholder="请选择">
+      <el-option v-for="item in options" :label="item.label" :value="item.value" :key="item.value" />
+    </el-drag-select>
+
+    <div style="margin-top:30px;">
+      <el-tag v-for="item of value" :key="item" style="margin-right:15px;">{{ item }}</el-tag>
+    </div>
+
+  </div>
+</template>
+
+<script>
+import ElDragSelect from '@/components/DragSelect' // base on element-ui
+
+export default {
+  name: 'DragSelectDemo',
+  components: { ElDragSelect },
+  data() {
+    return {
+      value: ['Apple', 'Banana', 'Orange'],
+      options: [{
+        value: 'Apple',
+        label: 'Apple'
+      }, {
+        value: 'Banana',
+        label: 'Banana'
+      }, {
+        value: 'Orange',
+        label: 'Orange'
+      }, {
+        value: 'Pear',
+        label: 'Pear'
+      }, {
+        value: 'Strawberry',
+        label: 'Strawberry'
+      }]
+    }
+  }
+}
+</script>