Provide a flake.nix?

[autra]

The documented default installation asks to download and install manually a file in a config folder. This breaks the declarative aspect of nixos. As flox already uses nix under the hood, it looks natural to provide a declarative way of installing flox-direnv.

Among the possibility, there are at least:

• a flake.nix
• or a "home-manager" snippet
• maybe there is a pure nix possibility?

Thanks in advance!

[tomberek]

Might not be needed as it might be in upstream direnv at some point: direnv/direnv#1372