Add instructions to use with zoffline

[oldnapalm]

I understand if you don't want to merge this because it's unofficial, but just in case...

30

[netbrain]

Yeah, I don't feel like adding official support for zoffline, not for the time being at least.

But how about you add this under show and tell instead?

https://github.com/netbrain/zwift/discussions/categories/show-and-tell

In any case I feel like this warrants its own Docker image and has its own GitHub actions to build this image. Probably tagged as a variant like netbrain/Zwift:offline-1.50.0

I'll reconsider it if you add this automation as well 😅🫣