Add minimal-versions CI

[NobodyXu]

Help discover bugs in version requ
irements

[NobodyXu]

cc @Byron seems like libz-sys is ok?

I'm not sure if I'm running with the right feature set

[Byron]

Even though it says it uses minimal versions, I am missing cargo update with minimal versions set. Right now it would use Cargo.lock or the latest available, I think.

[NobodyXu]

Thanks, I was braindead when writing this 😂

[Byron]

I tried to get the actual Cargo-zng.toml file tested as well, but on Windows it's failing as it appears to be unable to find visual studio related environment variables, and I couldn't figure out why.
So I just left it untested, but applied the expected fix anyway.

Once CI is green I can create a new release and then fix flate2, which ultimately fixes gitoxide.