function saveToFile(filename, data) {
  const fs = require("fs");
  if (fs.existsSync(filename)) {
    return console.error(`File "${filename}" exists!`);
  }

  fs.writeFileSync(filename, data);
}
Write the json with account information to a file
so it can be uploaded to other password managers etc easily.

@param {String} data A `JSON.stringify`ed list of accounts.