docs: add lightbox docs

Change-Id: I736b5710e75f7b02ef6260af4c2081a54e6d0981

one/docs/demo/lightbox/default.vue

@@ -0,0 +1,83 @@
+<template>
+<article>
+  <div>
+    <veui-check-box
+      v-model="wrap"
+    >循环播放</veui-check-box>
+    <veui-check-box
+      v-model="indicator"
+      true-value="number"
+      false-value="none"
+    >头部页码</veui-check-box>
+  </div>
+  <veui-button
+    class="mt-3p"
+    ui="primary"
+    @click="open = true"
+  >展现灯箱</veui-button>
+  <veui-lightbox
+    :open.sync="open"
+    :datasource="items"
+    :wrap="wrap"
+    :indicator="indicator"
+  />
+</article>
+</template>
+
+<script>
+import { Lightbox, Checkbox, Button } from 'veui'
+
+export default {
+  components: {
+    'veui-lightbox': Lightbox,
+    'veui-check-box': Checkbox,
+    'veui-button': Button
+  },
+  data () {
+    return {
+      wrap: false,
+      indicator: 'number',
+      open: false
+    }
+  },
+  computed: {
+    items() {
+      return [
+        {
+          src:
+            'https://ecmb.bdimg.com/public01/one-design/2b77cc4a4c5c906993c0e512f3ddaf03.jpg',
+          alt: 'A cute kitty looking at you with its greenish eyes.',
+          desc: 'Cat'
+        },
+        {
+          src:
+            'https://ecmb.bdimg.com/public01/one-design/6fedc62b9221846ce5114c7447622e47.jpeg',
+          alt: 'A common kingfisher flying above river.',
+          desc: 'Kingfisher'
+        },
+        {
+          src: 'https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.webm',
+          alt: 'flower video',
+          desc: '花',
+          type: 'video'
+        },
+        {
+          src:
+            'https://ecmb.bdimg.com/public01/one-design/e1b6473c898d9e456452ee79d7533a86.jpeg',
+          alt: 'A white and gray dolphin in blue water.',
+          desc: 'Dolphin'
+        }
+      ]
+    }
+  }
+}
+</script>
+
+<style lang="less" scoped docs>
+.veui-checkbox {
+  margin-right: 15px;
+}
+.mt-3p {
+  margin-top: 12px;
+}
+</style>