Add Nix devshell flake (#138)

Author: glasgow-haskell-omelette

flake.lock

@@ -0,0 +1,11 @@
+{
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  outputs = {nixpkgs, ...}: {
+    devShell = nixpkgs.lib.genAttrs (nixpkgs.legacyPackages.x86_64-linux.onnxruntime.meta.platforms) (system: let
+      pkgs = nixpkgs.legacyPackages.${system};
+    in
+      pkgs.mkShell {
+        packages = with pkgs; [onnxruntime openssl pkg-config rustPlatform.bindgenHook];
+      });
+  };
+}