doc: add flake

and test in CI via nixci

doc/flake.nix

@@ -0,0 +1,36 @@
+{
+  nixConfig = {
+    extra-substituters = "https://srid.cachix.org";
+    extra-trusted-public-keys = "srid.cachix.org-1:3clnql5gjbJNEvhA/WQp7nrZlBptwpXnUk6JAv8aB2M=";
+  };
+
+  inputs = {
+    emanote.url = "github:srid/emanote";
+    nixpkgs.follows = "emanote/nixpkgs";
+    flake-parts.follows = "emanote/flake-parts";
+  };
+
+  outputs = inputs@{ self, flake-parts, nixpkgs, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } {
+      systems = nixpkgs.lib.systems.flakeExposed;
+      imports = [ inputs.emanote.flakeModule ];
+      perSystem = { self', pkgs, system, ... }: {
+        emanote = {
+          # By default, the 'emanote' flake input is used.
+          # package = inputs.emanote.packages.${system}.default;
+          sites."default" = {
+            layers = [ ./. ];
+            layersString = [ "." ];
+            port = 8181;
+            prettyUrls = true;
+          };
+        };
+        devShells.default = pkgs.mkShell {
+          buildInputs = [
+            pkgs.nixpkgs-fmt
+          ];
+        };
+        formatter = pkgs.nixpkgs-fmt;
+      };
+    };
+}

flake.nix

@@ -23,6 +23,9 @@
       dev = {
         dir = "./dev";
       };
+      doc = {
+        dir = "./doc";
+      };
     };
   };
 }