add npm keyword info

package.json

 {
   "name": "NeteaseCloudMusicApi",
-  "version": "2.1.5",
-  "description": "",
+  "version": "2.1.6",
+  "description": "网易云音乐 NodeJS 版 API",
   "scripts": {
     "start": "node app.js",
     "test": "mocha -r intelli-espower-loader -t 20000 test"
   },
-  "keywords": [],
+  "keywords": ["网易云音乐","网易云","音乐","网易云音乐nodejs"],
   "author": "",
   "license": "MIT",
   "dependencies": {