feat(nix): generate module options docs and sync to website

- Add nix/generate-hm-options.nix to export HM and NixOS module options as JSON via nixosOptionsDoc
- Expose hm-options-json and nixos-options-json packages in flake.nix
- Add CI workflow to auto-build and push JSONs to mangowm.github.io on module changes
- Add missing description to hm-modules enable option

nix/generate-options.nix

@@ -0,0 +1,28 @@
+self:
+{
+  pkgs,
+  lib ? pkgs.lib,
+  module,
+  optionPrefix,
+}:
+let
+  eval = lib.evalModules {
+    modules = [
+      (import module self)
+      { _module.check = false; }
+    ];
+    specialArgs = { inherit pkgs; };
+  };
+
+  optionsDoc = pkgs.nixosOptionsDoc {
+    options = eval.options;
+    transformOptions =
+      opt:
+      opt
+      // {
+        visible = opt.visible && !opt.internal;
+        name = lib.removePrefix optionPrefix opt.name;
+      };
+  };
+in
+optionsDoc.optionsJSON

nix/hm-modules.nix

@@ -22,6 +22,7 @@ in
       enable = mkOption {
         type = types.bool;
         default = false;
+        description = "Whether to enable mangowm, a Wayland compositor based on dwl.";
       };
       package = lib.mkOption {
         type = lib.types.package;