Add nix flake

flake.nix

@@ -0,0 +1,32 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    rust-overlay.url = "github:oxalica/rust-overlay";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+  outputs =
+    inputs:
+    inputs.flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        overlays = [ inputs.rust-overlay.overlays.default ];
+        pkgs = import inputs.nixpkgs { inherit system overlays; };
+        rust = pkgs.rust-bin.stable.latest.default;
+        rust-analyzer = pkgs.rust-analyzer;
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = [
+            rust
+            rust-analyzer
+          ];
+          shellHook = ''
+            export CARGO_HOME="$PWD/.cargo"
+            export PATH="$CARGO_HOME/bin:$PATH"
+            mkdir -p .cargo
+            echo '*' > .cargo/.gitignore
+          '';
+        };
+      }
+    );
+}