add flake.nix

flake.nix

@@ -0,0 +1,35 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs";
+    systems.url = "github:nix-systems/default-linux";
+    esp-idf.url = "github:mirrexagon/nixpkgs-esp-dev?rev=6c34f2436015eb6c107970d9b88f3d5d4600c6fa";
+  };
+
+  outputs = { nixpkgs, systems, esp-idf, ... }: let
+    inherit (nixpkgs) lib;
+    eachSystem = lib.genAttrs (import systems);
+    pkgsFor = eachSystem (system:
+      import nixpkgs {
+        inherit system;
+      });
+  in {
+    devShells = eachSystem(system: let
+      inherit (esp-idf.packages.${system}) esp-idf-esp32;
+      pkgs = pkgsFor.${system};
+    in {
+      default = pkgs.mkShell {
+        inputsFrom = [
+          # for building and flashing the sketch
+          esp-idf-esp32
+        ];
+
+        packages = [
+          esp-idf-esp32
+
+          # for the `fontconvert.py` script of epdiy
+          (pkgs.python3.withPackages(ps: [ps.freetype-py]))
+        ];
+      };
+    });
+  };
+}