decryptPhrase function
This function does to phrases what their counterparts do to words.
Implementation
String decryptPhrase(int factor, String encryptedPhrase) {
List<String> decryptedWords = [];
List<String> wordList = encryptedPhrase.split('=>');
for (var i = 0; i < wordList.length; i++) {
String result = decryptWord(factor, wordList[i]);
decryptedWords.add(result);
}
String newlyDecryptedString = decryptedWords.join(' ');
return newlyDecryptedString;
}