caesarCipherEncrypt = (str, shift, alphabet = englishAlphabet) => {
  // Create a cipher map:
  const cipherMap = getCipherMap(alphabet, shift);
  return str
    .toLowerCase()
    .split('')
    .map((char) => cipherMap[char] || char)
    .join('');
}
@param {string} str
@param {number} shift
@param {string[]} alphabet
@return {string}