feat: add initial flake configuration and .envrc file

.envrc

@@ -0,0 +1 @@
+use flake

flake.nix

@@ -0,0 +1,30 @@
+{
+  description = "Hotel-Manager";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs, ... }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+    in
+    {
+      devShells.${system}.default =
+        pkgs.mkShell
+          {
+            buildInputs = [
+              pkgs.nodePackages."@angular/cli"
+              pkgs.git
+            ];
+
+            RUST_SRC_PATH = "${pkgs.rust.packages.stable.rustPlatform.rustLibSrc}";
+
+            shellHook = ''
+export CARGO_HOME=$HOME/.cargo
+export RUSTUP_HOME=$HOME/.rustup
+            '';
+          };
+    };
+}