Adds tzdata to properly handle timezones

[jeroenj]

This makes it possible to for example use Europe/Brussels as the timezone. Reason for this is that without it it seems to be impossible to set it to the correct timezone:

bash-5.0# TZ=CET
bash-5.0# date
Mon Oct 28 21:16:38 CET 2019

bash-5.0# TZ=Europe/Brussels
bash-5.0# date
Mon Oct 28 21:16:59 UTC 2019

bash-5.0# apk add tzdata
(1/1) Installing tzdata (2019c-r0)
Executing busybox-1.30.1-r2.trigger
OK: 55 MiB in 64 packages

bash-5.0# TZ=Europe/Brussels
bash-5.0# date
Mon Oct 28 22:17:47 CET 2019

[dperson]

Thanks it's been merged.