Add Nix flake to biscuit-cli

Author: er4hn

flake.lock

@@ -0,0 +1,36 @@
+{
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    naersk.url = "github:nix-community/naersk";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, flake-utils, naersk, nixpkgs }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = (import nixpkgs) {
+          inherit system;
+        };
+
+        naersk' = pkgs.callPackage naersk {};
+
+      in rec {
+        # For `nix build` & `nix run`:
+        defaultPackage = naersk'.buildPackage {
+          src = ./.;
+        };
+
+        # For `nix develop`:
+        devShell = pkgs.mkShell {
+          nativeBuildInputs = with pkgs; [
+		cargo
+		clippy
+		libiconv
+		rustc
+		rustfmt
+		rust-analyzer
+		];
+        };
+      }
+    );
+}