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(`-`).

modules/darwin/wm/skhd.nix

@@ -1,6 +1,6 @@
 {
   config,
-  username,
+  myvars,
   ...
 }: {
   services.skhd = {
@@ -10,7 +10,7 @@
 
   # custom log path for debugging
   launchd.user.agents.skhd.serviceConfig = let
-    homeDir = config.users.users."${username}".home;
+    homeDir = config.users.users."${myvars.username}".home;
   in {
     StandardErrorPath = "${homeDir}/Library/Logs/skhd.stderr.log";
     StandardOutPath = "${homeDir}/Library/Logs/skhd.stdout.log";