add flake.nix to allow building/developing within nix develop

flake.lock

@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1659877975,
+        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1664106353,
+        "narHash": "sha256-HMJP80+DSxFySpWyuxz5+iNozS3+dVt0b4n6YMIU5/8=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "79d3ca08920364759c63fd3eb562e99c0c17044a",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "ref": "nixos-unstable",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,20 @@
+{
+  description = "TODO";
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-unstable";
+    flake-utils.url = github:numtide/flake-utils;
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    with flake-utils.lib; eachSystem allSystems (system:
+    let
+      pkgs = import nixpkgs {
+        inherit system;
+      };
+    in
+    rec {
+      devShells.default = with pkgs; mkShell {
+        buildInputs = [ flutter ];
+      };
+    });
+}