added a .timezone(name, utc_offset_minutes) query option
fixes: #25
You can test it with the --timezone CLI parameter (note: the CLI needs to be compiled with --features timezone).
The timezone library adds about 2MB to the CLI binary size.
If you are just using your local timezone, you should not need a timezone database, since timezone name and offset can be queried through the OS (and yes, you need to send both to the YouTube API for it to work. Omitting the timezone name results in YouTube falling back to UTC.