Library version constraints

[ianprime0509]

GIR has metadata indicating which version of a library introduced an API. To make it easier for users to remain compatible with older library versions, it would be nice to expose this in a way that allows users to exclude APIs from newer versions.

A rough idea of how this might be done is something like

pub const someBinding = if (comptime max_version.supports("4.10")) contentOfBinding else @compileError("Only supported in GTK 4.10 and later");