Add a nix flake to build the app

flake.nix

@@ -0,0 +1,28 @@
+{
+	description = "An app which reads data from a serial port and serves it on a TCP port.";
+
+	inputs = {
+		nixpkgs.url = github:NixOS/nixpkgs/nixos-23.05;
+		flake-utils.url = "github:numtide/flake-utils";
+	};
+
+	outputs = { self, nixpkgs, flake-utils, ... }: flake-utils.lib.eachDefaultSystem (system:
+		let
+			pkgs = import nixpkgs { inherit system; };
+			main-package = (with pkgs; stdenv.mkDerivation {
+				pname = "serial-to-tcp";
+				version = "1.0.1";
+				src = self;
+				nativeBuildInputs = [
+					rustc
+					cargo
+				];
+				buildPhase = "cargo build";
+				installPhase = "mkdir -p $out/bin; install -t $out/bin target/debug/serial-to-tcp";
+			});
+		in rec {
+			defaultApp = flake-utils.lib.mkApp { drv = defaultPackage; };
+			defaultPackage = main-package;
+		}
+	);
+}