Prettier: Update Cheat Sheet

[coolaj86]

We need to add the dependency-free prettier usage to the cheat sheet:

{
    "scripts": {
        "prettier": "npx prettier@2.x -w '**/*.{md,js,html,css}'"
    }
}

npm run prettier

We also need to add some sort of prettier-init that automatically adds that line and the .prettierrc.json and .prettierignore to current repo.