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(`-`).

hosts/12kingdoms-shoukei/brcm-firmware/default.nix

@@ -0,0 +1,10 @@
+{pkgs, ...}:
+pkgs.stdenvNoCC.mkDerivation {
+  name = "brcm-firmware";
+  nativeBuildInputs = with pkgs; [gnutar xz];
+  buildCommand = ''
+    dir="$out/lib/"
+    mkdir -p "$dir"
+    tar -axvf ${./firmware.tar.xz} -C "$dir"
+  '';
+}