prettier formatting directives for package.json files.

prettier.json

{
"prettier": {
    "arrowParens": "always",
    "bracketSpacing": true,
    "endOfLine": "lf",
    "htmlWhitespaceSensitivity": "css",
    "jsxBracketSameLine": false,
    "jsxSingleQuote": false,
    "semi": true,
    "singleQuote": true,
    "tabWidth": 2
  },
}