Add nix setup for development and upgrade node

Author: airhorns

.envrc

@@ -0,0 +1,3 @@
+use flake
+
+source_env_if_exists .envrc.local

.github/actions/setup-test-env/action.yml

@@ -8,13 +8,13 @@ runs:
       - name: Install Node.js
         uses: actions/setup-node@v3
         with:
-          node-version: 16
+          node-version: 21
 
       - uses: pnpm/action-setup@v2
         name: Install pnpm
         id: pnpm-install
         with:
-          version: 7
+          version: 8
           run_install: false
 
       - name: Get pnpm store directory

.gitignore

@@ -1,6 +1,8 @@
+.direnv
 dist
 node_modules
 yarn.lock
 vscode-profile*
 isolate-*
-flamegraph.html
+flamegraph.html
+*.perf

Benchmarking.md

@@ -35,7 +35,7 @@ node --prof-process isolate-*.log
 You can postprocess the generated `isolate-0x<something>.log` file into the data `flamegraph` expects, and then feed it to `flamegraph` to see a visual breakdown of performance. You can do that in one command like so:
 
 ```shell
-node --prof-process --preprocess -j isolate-*.log | p flamebearer
+node --prof-process --preprocess -j isolate-*.log | pnpm flamebearer
 ```
 
 #### CPU profiling with VSCode

flake.lock

@@ -0,0 +1,33 @@
+{
+  description = "mobx-quick-tree development environment";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, flake-utils, nixpkgs }:
+    (flake-utils.lib.eachSystem [
+      "x86_64-linux"
+      "x86_64-darwin"
+      "aarch64-darwin"
+    ]
+      (system: nixpkgs.lib.fix (flake:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+        in
+        rec {
+
+          packages =
+            rec {
+              bash = pkgs.bash;
+              nodejs = pkgs.nodejs_21;
+              pnpm = pkgs.nodejs_21.pkgs.pnpm;
+            };
+
+          devShell = pkgs.mkShell {
+            packages = builtins.attrValues packages;
+          };
+        }
+      )));
+}