Add TimeZones iCal Library to Calendar

The TimeZones iCal Library holds API endpoints to GET a list of IANA time zones; and can also GET corresponding ical VTIMEZONE blocks as ics file response to include in any .ica iCal file

README.md

@@ -350,6 +350,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Non-Working Days](https://github.com/gadael/icsdb) | Database of ICS files for non working days | No | Yes | Unknown |
 | [Non-Working Days](https://isdayoff.ru) | Simple REST API for checking working, non-working or short days for Russia, CIS, USA and other | No | Yes | Yes |
 | [Russian Calendar](https://github.com/egno/work-calendar) | Check if a date is a Russian holiday or not | No | Yes | No |
+| [TimeZones iCal Library](https://tz.add-to-calendar-technology.com/) | Database of official time zones and corresponding iCal VTIMEZONE blocks | No | Yes | Unknown |
 | [UK Bank Holidays](https://www.gov.uk/bank-holidays.json) | Bank holidays in England and Wales, Scotland and Northern Ireland | No | Yes | Unknown |
 
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