Generate docs (#1)

* feat: Reorganize code

* feat: Generate docs as mdbook

* feat: Add deploy github action

* fix: formatting

docs/default.nix

@@ -0,0 +1,16 @@
+{ pkgs, lib, ... }:
+let
+  eval = lib.evalModules { modules = [ ../options.nix ]; };
+  doc = (pkgs.nixosOptionsDoc { inherit (eval) options; }).optionsCommonMark;
+in
+pkgs.stdenvNoCC.mkDerivation {
+  name = "nixos-configuration-book";
+  src = ./.;
+
+  patchPhase = ''
+    # copy generated options removing the declared by statement
+    sed '/^\*Declared by:\*$/,/^$/d' <${doc} >> src/options.md
+  '';
+
+  buildPhase = "${pkgs.mdbook}/bin/mdbook build --dest-dir $out";
+}