chore: update devcontainer config (#62)

* chore: modernize devcontainer config for better DX

Replace unused JSHint feature with ESLint/Prettier/DotENV extensions,
switch to npm ci, auto-create .env from template, add VS Code settings,
run as non-root user, and display onboarding steps on container start.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: update readme with dev container section

* fix: use postattachcommand so message is shown to user on startup

* chore: move welcome message to script with docs link

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: thephez

.devcontainer/devcontainer.json

@@ -1,26 +1,27 @@
-// For format details, see https://aka.ms/devcontainer.json. For config options, see the
-// README at: https://github.com/devcontainers/templates/tree/main/src/javascript-node
 {
-	"name": "Tutorials",
-	"image": "mcr.microsoft.com/devcontainers/javascript-node:20",
-	"features": {
-    "ghcr.io/devcontainers-contrib/features/jshint:2": {}
-  },
+  "name": "Dash Platform Tutorials",
+  "image": "mcr.microsoft.com/devcontainers/javascript-node:20",
+  "remoteUser": "node",
 
-  // Use 'forwardPorts' to make a list of ports inside the container available locally.
-  // "forwardPorts": [],
+  "onCreateCommand": "cp -n .env.example .env",
+  "postCreateCommand": "npm ci",
+  "postAttachCommand": ".devcontainer/welcome.sh",
 
-  // Use 'postCreateCommand' to run commands after the container is created.
-  "postCreateCommand": "npm install",
-
-  // Configure tool-specific properties.
   "customizations": {
-    // Configure properties specific to VS Code.
     "vscode": {
-      // Add the IDs of extensions you want installed when the container is created.
       "extensions": [
+        "dbaeumer.vscode-eslint",
+        "esbenp.prettier-vscode",
+        "mikestead.dotenv",
         "streetsidesoftware.code-spell-checker"
-      ]
+      ],
+      "settings": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.tabSize": 2,
+        "files.eol": "\n",
+        "files.trimTrailingWhitespace": true,
+        "files.insertFinalNewline": true
+      }
     }
   }
 }

.devcontainer/welcome.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+printf '\n=== Dash Platform Tutorials ===\n\nNext steps:\n  1. Verify connection: node connect.mjs\n  2. Create a wallet:   node create-wallet.mjs\n  3. Edit .env with your mnemonic (PLATFORM_MNEMONIC)\n  4. Start tutorials in 1-Identities-and-Names/\n\nDocs: https://docs.dash.org/projects/platform/en/stable/docs/tutorials/introduction.html\n\n'

README.md

@@ -8,6 +8,20 @@ site](http://docs.dash.org/projects/platform/en/stable/docs/tutorials/introducti
 uses `@dashevo/evo-sdk`. For the legacy `js-dash-sdk` tutorials, see
 [v2.0.1](https://github.com/dashpay/platform-tutorials/releases/tag/v2.0.1).
 
+## Quick Start with Dev Containers
+
+[![Open in GitHub
+Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/dashpay/platform-tutorials)
+
+The included dev container provides a ready-to-use environment with Node.js, dependencies, and
+editor tooling pre-configured. Open the repo in [GitHub
+Codespaces](https://codespaces.new/dashpay/platform-tutorials) or locally with the [VS Code Dev
+Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers).
+
+On first launch the container installs dependencies and creates a starter `.env` file from
+`.env.example`. Run `node create-wallet.mjs` to generate a mnemonic, then set `PLATFORM_MNEMONIC`
+in your `.env` file to begin the tutorials.
+
 ## Install
 
 Note: [NodeJS](https://nodejs.org/en/download/) (v20+) must be installed to run the tutorial code.