feat: add ?.

Author: skillnull

README.md

@@ -12,13 +12,13 @@
 使用 UMD 格式
 <script src="https://www.unpkg.com/@skillnull/device-js@2.1.7/dist/device.js"></script>
 # or
-<script src="https://cdn.jsdelivr.net/npm/@skillnull/device-js@2.1.7/dist/device.js"></script>
+<script src="https://cdn.jsdelivr.net/npm/@skillnull/device-js@2.1.8/dist/device.js"></script>
 
 
 使用 ES 格式
-<script src="https://www.unpkg.com/@skillnull/device-js@2.1.7/dist/device.es.js" type="module"></script>
+<script src="https://www.unpkg.com/@skillnull/device-js@2.1.8/dist/device.es.js" type="module"></script>
 # or
-<script src="https://cdn.jsdelivr.net/npm/@skillnull/device-js@2.1.7/dist/device.es.js" type="module"></script>
+<script src="https://cdn.jsdelivr.net/npm/@skillnull/device-js@2.1.8/dist/device.es.js" type="module"></script>
 ```
 
 > #### 安装

dist/device.es.js

@@ -1,6 +1,6 @@
 {
   "name": "@skillnull/device-js",
-  "version": "2.1.7",
+  "version": "2.1.8",
   "description": "Get device information by javascript.",
   "main": "dist/device",
   "author": "skillnull",