Feature Request: allow searching for historical versions of packages

[panda2134]

It is relatively easy to install historical versions of packages in nixpkgs simply by appending the commit hash. However, it is rather difficult to find out which commit contains the specific version of a given package. There is already a third-party open source website that provides a webapp to achieve this. However, I guess it would be better for this feature to be directly integrated into nixos-search, so that users can easily install older versions of a package without googling for a solution.

FYI, the source code of the mentioned website is at https://github.com/lazamar/nix-package-versions