Consider supporting older versions of `libgit2`?

[madsmtm]

Hey, my package manager currently only has libgit2 version 1.3.0 available. I'm using MacPorts (on macOS 10.14.6), but if I'm not mistaken, Ubuntu 22.04 uses version 1.1.0.

I think it would be nice if this package could support older versions of libgit2 (up until a certain point ofc.), so that as users, we don't have to compile it.

I'm aware that https://github.com/rust-lang/git2-rs/pull/806 bumped the minimum version from 1.3.0 to 1.4.0 because newer features were needed, so I'm definitely not complaining about using newer features for better efficiency! I mostly just wanted to ask how big of an effort it would be to support older versions, and whether it is something that would be desired by this crate?