Add PL Silesian buses (Transport GZM)

[grzesjam]

Hello! 👋

ZTM TransportGZM is a public transport organization based in the Silesian Voivodeship, Poland. They manage buses, trams, trolleybuses and bikes.
ZTM is the organization that governs it, "TransportGZM" is a brand under which they run busses/trams/trolleybuses, and brand "TransportGZM MetroRower" is for bikes. That's the reason I picked o-transport~gzm~pl and f-transport~gzm~pl/o-transport~gzm~pl~tf

This PR adds ZTM TransportGZM GTFS and GTFS-RT.

• The GTFS-RT has a static URL. Licensed under CC-BY-4.0
• The GTFS doesn't have a static URL. I created an issue here but got no response, so I just went with creating a mirror for their data. Data is licensed under CC-BY-4.0

If something is missing or please let me know :)

[grzesjam]

TransportGZM has two versions of GTFS: "Normal" (apparently "temporary") and "Extended"
Data inside of them different, it has different fields in files.

I tried to push this directly to transitous but it had issue parsing "Extended" version and i had to use "normal" one.
I can't find anything about these extended and non-extended versions, which one should be used?

Both version can be checked out in Org i created with mirror https://github.com/orgs/TransportGZM-GTFS-mirror/repositories