update README

README.md

@@ -1 +1,63 @@
-# nix-command-utils
+# Nix Command Utils
+
+Helpers for defining commands for Nix shells under Flakes.
+
+## Quickstart
+
+``` nix
+{
+  inputs = {
+    command-utils.url = "github:expede/nix-command-utils";
+    flake-utils.url = "github:numtide/flake-utils";
+    # ...
+  };
+
+  outputs = {self, flake-utils, command-utils}:
+    flake-utils.lib.eachDefaultSystem (system: 
+      let
+        # Cargo just for example
+        cargo = "${pkgs.cargo}/bin/cargo";
+      
+        cmd = command-utils.cmd.${system};
+        command_menu = command-utils.commands.${system} {
+          hello = cmd "Print a hello world message" "echo 'Hello, world!'";
+
+          bench = cmd "Run benchmarks, including test utils"
+            "${cargo} bench --features test_utils";
+
+          "bench:host" = cmd "Run host Criterion benchmarks"
+            "${cargo} criterion";
+        };
+        #...
+      in
+        devShells.default = pkgs.mkShell {
+          nativeBuildInputs = with pkgs;
+            [
+              command_menu
+              # ...
+            ];
+            
+            #...
+        };
+      }
+    );
+}
+```
+
+``` console
+$ menu
+  ____                                          _
+ / ___|___  _ __ ___  _ __ ___   __ _ _ __   __| |___
+| |   / _ \| '_ ` _ \| '_ ` _ \ / _` | '_ \ / _` / __|
+| |__| (_) | | | | | | | | | | | (_| | | | | (_| \__ \
+ \____\___/|_| |_| |_|_| |_| |_|\__,_|_| |_|\__,_|___/
+
+
+bench      | Run benchmarks, including test utils
+bench:host | Run host Criterion benchmarks
+hello      | Print a hello world message
+
+$ hello
+Hello, world!
+```
+