 Add .prettierrc file

Needed for consistent formatting.

### Proposed Solution
`./.prettierrc`
```json
{
  "semi": true,
  "tabWidth": 2,
  "printWidth": 80,
  "singleQuote": false,
  "trailingComma": "es5",
  "bracketSpacing": true,
  "bracketSameLine": false,
  "arrowParens": "always",
  "endOfLine": "lf",
  "jsxSingleQuote": false
}
```