Feature Request: support for older version of PHPs

[LeslieLeung]

The older versions of PHPs is not supported by nix(see https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/aliases.nix) , so when I use devbox add php73, it promts Error: Package php73 not found..

However there are some workarounds, for example fossar/nix-phps . Is it possible for devbox to support such kind of workarounds?

[Lagoja]

We'll look into this! We're evaluating how to let users configure alternative Nix repositories and package sources for Devbox.

[Lagoja]

As of 0.4.7, we've released support for Nix Flakes in your package list. This means you can now install PHP versions from the fossar/nix-phps repo by adding the following to your packages list:

{
    "packages" : [
        "github:fossar/nix-phps#php73"
    ]
}

For more details, see https://www.jetpack.io/devbox/docs/guides/using_flakes/