Add Linter (code formatter)

[benoror]

• https://prettier.io/
• https://standardjs.com/

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• https://github.com/prettier/prettier#how-does-it-compare-to-eslint-or-tslint-stylelint
• https://github.com/sheerun/prettier-standard
• https://www.reddit.com/r/javascript/comments/6g8adf/prettier_has_surpassed_standard_as_mostdownloaded/
• https://testingjavascript.com/courses/static-analysis-testing-javascript-applications