Implement local dependencies for importAtom

[LiGoldragon]

Allows using a local manifest as dependency, with importAtom

# simple@.toml
[atom]
id = "simple"
version = "0.1.0"

[local.local-lib]
path = "local-lib@.toml"

# simple/mod.nix
{
  inherit (use.local-lib) simpleString;
}

# local-lib@.toml
[atom]
id = "local-lib"
version = "0.1.0"

# local-lib/mod.nix
{
  SimpleString = "A simple string";
}

[nrdxp]

the intended API for this basically boils down to generating a lock (with eka) and then consuming it on the Nix side according to some rules. Local dependencies are already implemented in the first draft:
#42

the manifest API is not currently stable, I have some wip code in eka