npm install 之后，packages.json 就自动添加了
比如 "mockjs": "^1.1.0",

"dependencies": {
"axios": "^0.18.0",
"cjs": "0.0.11",
"echarts": "^4.0.4",
"element-ui": "^2.3.6",
"forever-monitor": "^1.7.1",
"layui": "0.0.1",
"layui-src": "^2.2.5",
"mockjs": "^1.1.0",
"qs": "^6.5.2",
"react": "^16.3.2",
"vue": "^2.5.2",
"vue-resource": "^1.5.1",
"vue-router": "^3.0.1"
},