wrappers: add meta.wrappers options to wrappers

Allows the docs to be a little less hard-coded.

Lays the groundwork for splitting up the platform-specific option docs
on a per-page basis.

wrappers/modules/darwin.nix

@@ -1,3 +1,7 @@
 {
   imports = [ ./shared.nix ];
+
+  config = {
+    meta.wrapper.name = "nix-darwin";
+  };
 }

wrappers/modules/hm.nix

@@ -17,5 +17,6 @@
   config = {
     wrapRc = lib.mkOptionDefault false;
     impureRtp = lib.mkOptionDefault true;
+    meta.wrapper.name = "home-manager";
   };
 }

wrappers/modules/nixos.nix

@@ -5,4 +5,8 @@
   };
 
   imports = [ ./shared.nix ];
+
+  config = {
+    meta.wrapper.name = "NixOS";
+  };
 }

wrappers/modules/shared.nix

@@ -2,5 +2,13 @@
 {
   options = {
     enable = lib.mkEnableOption "nixvim";
+
+    meta.wrapper = {
+      name = lib.mkOption {
+        type = lib.types.str;
+        description = "The human-readable name of this nixvim wrapper. Used in documentation.";
+        internal = true;
+      };
+    };
   };
 }