refactor: Use haumea for filesystem-based module system for flake outputs

refactor: Use hyphen(`-`) for variable names & folder names(except Python), replace all unserscore(`_`) with hyphen(`-`).

lib/default.nix

@@ -3,6 +3,8 @@
   macosSystem = import ./macosSystem.nix;
   nixosSystem = import ./nixosSystem.nix;
   attrs = import ./attrs.nix {inherit lib;};
+  # use path relative to the root of the project
+  relativeToRoot = lib.path.append ../.;
   scanPaths = path:
     builtins.map
     (f: (path + "/${f}"))