This packages Limine in Nix and exports it via the Nix Flake.
Due to the nature of the project, i.e., the self-hacked
"git submodule checkout with additional patches" in `./bootstrap`,
packing this in a Nix-way is very complicated.
The big advantage of packaging Limine in Nix directly as part
of the flake (additionally to nixpkgs) is that instead of using a
fixed version from nixpkgs coming from a Limine release, one can
use the current source and build everything in Nix.
This inits a flake.nix into the repository that exports a convenient Nix shell.
When using `$ nix develop`, users will get a shell with all relevant tools to
build the repository. If one uses a "direnv" integration into their shell, the
environment is automatically loaded.
