Support nix flakes

Describe your feature request

I see that there is a blog post mentioning Nix flakes several times, however I don’t see any open posts here about supporting them.
See also: Nix flakes

What problem(s) would this feature solve?

Using nix flakes in a development environment. This might allow existing projects that use a flake.nix to be supported out of the box instead of requiring a special replit.nix file. Even other nix projects use shell.nix.

Explain what you were trying to do when you came across the problem leading to this feature request

I could be wrong but from what I’ve seen it only seems to support replit.nix and not flake.nix…