Consider getting timezone data from dart package "timezone"

[rich-j]

TimeMachine provides 3 major components: library, timezone data, culture data. The library is unsurpassed in providing correct datetime calculations. I'm glad to see TimeMachine getting NNBD conversion - and a lot more cleanup (thanks @SteveAlexander).

Going forward, the main ongoing maintenance need is updating the timezone data. Just wondering if it would make sense to use the timezone data from the package https://pub.dev/packages/timezone?