✨ Added experimental add-to-calendar feature (#64) #66

## REFER TO ICALENDAR STANDARD FOR DETAILS
This code is experimental several things need to be implemented for it to be complete:
1 )  Need to find out how to get the day for a given date, since ICS needs a specific date
2 ) recurring events works, even has a stop date. users should decide when to stop reminding.
3 ) replace the first code up until Future.wait to suit application needs.

lib/calTec.dart

@@ -0,0 +1,68 @@
+import 'dart:io';
+import 'dart:convert';
+import 'package:albiruni/albiruni.dart';
+import 'package:ical/serializer.dart';
+
+void main(List<String> args) async {
+  print("hello world");
+  var arr = ['AERO1121', 'AERO1322', 'AERO2128'];
+  Albiruni albiruni = Albiruni(semester: 2, session: "2022/2023");
+  var mappedArr = arr
+      .map((e) => albiruni.fetch("ENGIN", course: e.toAlbiruniFormat()))
+      .toList();
+  var result = await Future.wait(mappedArr);
+  result.map((e) => print(e)).toList();
+  if(result.isNotEmpty){
+    var class_appointments = result.map((e) => GenerateCalData(e)).toList();
+    var serialized_calendar_data = class_appointments.map((e) => e.serialize()).toList();
+    var file = new File('test.ics');
+    var _ = serialized_calendar_data.map((e) => file.writeAsStringSync(e, mode: FileMode.append)).toList();
+  }
+
+}
+
+ICalendar GenerateCalData(List<Subject> item) {
+  ICalendar cal = ICalendar();
+  //IF SUBJECT HAS MORE THAN TWO DATES
+  if (item.single.dayTime.length > 1) {
+    for (var element in item.single.dayTime) {
+      cal.addElement(
+        IEvent(
+          uid: 'test@example.com',
+          start: DateTime(2023,3,6,),
+          url: 'https://pub.dartlang.org/packages/srt_parser',
+          status: IEventStatus.CONFIRMED,
+          location: 'IIUM',
+          description:
+              'COURSE TITLE:${item.single.title}\nCREDIT HOUR:${item.single.chr}\nVENUE:${item.single.venue}\nLECTURERS:\n${item.single.lect.map((e) => print(e+"\n"))}',
+          summary: item.single.code,
+          //FOR RECURRENCE UNTIL DATE, ASK INPUT FROM USER
+          rrule: IRecurrenceRule(
+              frequency: IRecurrenceFrequency.WEEKLY,
+              untilDate: DateTime(2023, 6, 6)),
+        ),
+      );
+    }
+    return cal;}
+
+  cal.addElement(
+    IEvent(
+      uid: 'test@example.com',
+      start: DateTime(
+        2023,
+        3,
+        6,
+      ),
+      url: 'https://pub.dartlang.org/packages/srt_parser',
+      status: IEventStatus.CONFIRMED,
+      location: 'IIUM',
+      description:
+          'COURSE TITLE:${item.single.title}\nCREDIT HOUR:${item.single.chr}\nVENUE:${item.single.venue}',
+      summary: item.single.code,
+      rrule: IRecurrenceRule(
+          frequency: IRecurrenceFrequency.WEEKLY,
+          untilDate: DateTime(2023, 6, 6)),
+    ),
+  );
+  return cal;
+}