docs: function sentenceCase(sentence, exciting = false) {
  
    // uppercase the first letter
    sentence = sentence[0].toUpperCase() + sentence.slice(1);
  
    if (['.', '!', '?'].indexOf(sentence.slice(-1)) > -1) {
      return sentence;
    } else if (exciting) {
      return sentence + "!";
    } else {
      return sentence + ".";
    }
  }