nix development shell

[ProducerMatt]

A Nix development shell creates identical development environments for anybody with Nix installed, so long as they run nix develop -f shell.nix in the root directory. It would be quite useful as I see from the chat, lots of time is spent working on just getting Node and Python to play nicely in traditional operating systems. This is the start of such a shell, but I don't know your project (and am not a Nix expert despite using it exclusively), so it's lacking at the moment. Any ideas or changes are appreciated.

Immediate concerns:

• Python app starts, but I haven't tested it.
• Node side requires next be available as a CLI app, but Nix isn't making it available. I'm using node2nix to make the Node support, maybe that's just not what it does. Regardless, if you manually npm i next in ./web/, the app starts. I haven't tested it.

Slightly less immediate concerns:

• node2nix can't import the package lockfile because it doesn't support lockfile version v3. But it still gets the versions from the package.json at least.
• node2nix leaves multiple Nix files in the ./web/ directory. Maybe they could at least be moved somewhere, but it would be nice to avoid them entirely.
• it's not a Nix flake, meaning it doesn't have a lockfile for Nix packages themselves. The lock files for Python and Node heavily reduce the risk for breakage though.