chore(package): update prettier to version 2.0.4

Closes #6

Author: greenkeeper[bot]

package.json

@@ -56,7 +56,7 @@
     "node-sass": "^4.13.1",
     "npm-run-all": "^4.1.5",
     "postcss-loader": "^3.0.0",
-    "prettier": "^1.19.1",
+    "prettier": "^2.0.4",
     "progress-bar-webpack-plugin": "^2.1.0",
     "qiniu": "^7.3.0",
     "sass-loader": "^8.0.2",