Add all of iogamaster modules

modules/nixos/system/env/default.nix

@@ -0,0 +1,42 @@
+{
+  options,
+  config,
+  lib,
+  ...
+}:
+with lib;
+with lib.frajul; let
+  cfg = config.system.env;
+in {
+  options.system.env = with types;
+    mkOption {
+      type = attrsOf (oneOf [str path (listOf (either str path))]);
+      apply = mapAttrs (_n: v:
+        if isList v
+        then concatMapStringsSep ":" toString v
+        else (toString v));
+      default = {};
+      description = "A set of environment variables to set.";
+    };
+
+  config = {
+    environment = {
+      sessionVariables = {
+        XDG_CACHE_HOME = "$HOME/.cache";
+        XDG_CONFIG_HOME = "$HOME/.config";
+        XDG_DATA_HOME = "$HOME/.local/share";
+        XDG_BIN_HOME = "$HOME/.local/bin";
+        # To prevent firefox from creating ~/Desktop.
+        XDG_DESKTOP_DIR = "$HOME";
+      };
+      variables = {
+        # Make some programs "XDG" compliant.
+        LESSHISTFILE = "$XDG_CACHE_HOME/less.history";
+        WGETRC = "$XDG_CONFIG_HOME/wgetrc";
+      };
+      extraInit =
+        concatStringsSep "\n"
+        (mapAttrsToList (n: v: ''export ${n}="${v}"'') cfg);
+    };
+  };
+}