chore: Add flake and direnv stuff

flake.nix

@@ -0,0 +1,40 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  };
+
+  outputs = {nixpkgs, ...}: let
+    systems = ["aarch64-darwin" "x86_64-linux"];
+    eachSystem = function:
+      nixpkgs.lib.genAttrs systems (system:
+        function {
+          inherit system;
+          pkgs = nixpkgs.legacyPackages.${system};
+        });
+  in {
+    devShells = eachSystem ({pkgs, ...}: {
+      default = pkgs.mkShellNoCC {
+        packages = [
+          # general deps
+          pkgs.nodejs_24
+          pkgs.pnpm_10
+
+          # wasm/rust stuff
+          pkgs.rustc
+          pkgs.cargo
+          pkgs.rust-analyzer
+          pkgs.rustfmt
+          pkgs.wasm-bindgen-cli
+          pkgs.wasm-pack
+          pkgs.lld
+
+          # frontend
+          pkgs.vscode-langservers-extracted
+          pkgs.typescript-language-server
+          pkgs.prettier
+          pkgs.tailwindcss-language-server
+        ];
+      };
+    });
+  };
+}