sys: added shell.nix

shell.nix helpls me to install enviromen in my local workdir

shell.nix

@@ -0,0 +1,11 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    cargo
+    rustc
+    rustfmt
+    clippy
+    rust-analyzer
+  ];
+}