Added manpages to the generated documentation

docs/man/default.nix

@@ -0,0 +1,30 @@
+{ pkgs, self, ... }:
+{
+  build = type: subcomponent: json:
+    pkgs.runCommand "hylonix-${subcomponent}-manpage"
+      {
+        header = ./header.5;
+        footer = ./footer.5;
+        inherit type subcomponent json;
+        revision = self.lastModifiedDate;
+
+        nativeBuildInputs = [
+          pkgs.buildPackages.installShellFiles
+          pkgs.nixos-render-docs
+        ];
+        allowedReferences = [ "out" ];
+      }
+      ''
+        substitute "$header" ./header \
+          --subst-var subcomponent \
+          --subst-var type
+
+        nixos-render-docs -j $NIX_BUILD_CORES options manpage \
+          --revision "$revision" \
+          --header ./header \
+          --footer "$footer" \
+          "$json/share/doc/nixos/options.json" \
+          "hylonix-$subcomponent.5"
+        installManPage hylonix-*.5
+      '';
+}