feat: nix direnv (#1367)

## Description

run `direnv allow` and all the nix packages in `flake.nix` will be
injected into your shell

## Testing

Explain the quality checks that have been done on the code changes

## Additional Information

- [x] I read the [contributing docs](../docs/contributing.md) (if this
is your first contribution)

Your ENS/address:

esm.eth

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
	- Integrated `Direnv` for improved environment variable management.
- Enhanced file association for `.envrc` with syntax highlighting in
Visual Studio Code.
- Added `direnv` to package dependencies for streamlined development
setups.

- **Bug Fixes**
- Updated `.gitignore` to exclude `.direnv` files, improving project
cleanliness.

- **Documentation**
- Updated recommended extensions in Visual Studio Code to support better
Nix syntax.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.envrc

@@ -0,0 +1,2 @@
+use flake
+export DIRENV_WARN_TIMEOUT=1m

.gitignore

@@ -59,3 +59,4 @@ Thumbs.db
 .zshrc
 /target
 _
+.direnv

.vscode/extensions.json

@@ -10,7 +10,7 @@
     // there is no angular in this repo!
     // but this is useful for running nx commands in vscode
     "nrwl.angular-console",
-    "antfu.vite"
+    "jeff-hykin.better-nix-syntax"
   ],
   "unwantedRecommendations": [
     // we use biome for linting and formatting

.vscode/settings.json

@@ -29,6 +29,7 @@
   },
   "files.associations": {
     ".gas-snapshot": "julia",
-    "base.json": "jsonc"
+    "base.json": "jsonc",
+    ".envrc": "dotenv"
   }
 }

flake.nix

@@ -23,6 +23,7 @@
           pkgs.nodejs_22
           pkgs.nodePackages.pnpm
           pkgs.bun
+          pkgs.direnv
           pkgs.foundry-bin
           pkgs.rust-bin.stable.latest.default # or pkgs.rust-bin.beta.latest.default
         ];