Add flake

flake.nix

@@ -0,0 +1,13 @@
+{
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-23.05";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+  outputs = { self, nixpkgs, flake-utils, ... }:
+    let
+      kernel = nixpkgs.linuxPackages_latest;
+    in
+    flake-utils.lib.eachDefaultSystem (system: {
+      packages.${system}.ethercat = (import ./ethercat.nix) { inherit kernel; };
+    });
+}