[Feature Request]: Add tzdef to Device Config

[rcarteraz]

Description

tzdef is missing from the device config menu. This allows users to set their timezone offset so device will display local time.

This is set using the appropriate string for your region. https://github.com/nayarsystems/posix_tz_db/blob/master/zones.csv

The apple client will actually handle this for you and display your timezone based on the device so all you have to do is save it. This would be a great way to handle it in the web too if possible. https://github.com/meshtastic/Meshtastic-Apple/blob/main/Meshtastic/Extensions/TimeZone.swift

[Hunter275]

https://github.com/meshtastic/protobufs/blob/master/meshtastic/config.proto#L187