capitalize function 
 
    
    
    
  Implementation
  String capitalize(String text) {
  String capitalized = "";
  List<String> sentences = text.split(RegExp(r'(?<=[.!?])\s*'));
  // '${sentence[0].toUpperCase()}${sentence.substring(1)}'
  for (int i = 0; i < sentences.length; i++) {
    String sentence = sentences[i];
    if (sentence.isNotEmpty) {
      if (i == sentences.length - 1) {
        capitalized += '${sentence[0].toUpperCase()}${sentence.substring(1)}';
      } else {
        capitalized += '${sentence[0].toUpperCase()}${sentence.substring(1)} ';
      }
    }
  }
  return capitalized;
}