build(deps): raise minimum node.js version

The minimum required Node.js version has been updated from `18.x` to `20.x`.
This change is reflected in `package.json`, `README.md`, and the CI
workflow. The CI matrix now tests against Node.js `20.x`, `22.x`, and `24.x`,
removing support for older versions.

BREAKING CHANGE: Node.js 18.x is no longer supported. Users must upgrade to
Node.js 20.x or higher.

Author: bitsnaps

.github/workflows/npm-build.yml

@@ -9,7 +9,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: ['18.x', '20.x', '23.x']
+        node-version: ['20.x', '22.x', '24.x']
     steps:
     - uses: actions/checkout@v4
     - name: Install pnpm

README.md

@@ -36,7 +36,7 @@ The **Puter CLI** is a command-line interface tool designed to interact with the
 ## Installation
 
 ### Prerequisites
-- Node.js (v18 or higher)
+- Node.js (v20 or higher)
 - npm (v7 or higher)
 
 Run the following command to install puter-cli globally in your system:

package.json

@@ -16,7 +16,7 @@
     "coverage": "TZ=UTC vitest run --coverage"
   },
   "engines": {
-    "node": ">=18.0.0"
+    "node": ">=20.0.0"
   },
   "keywords": [
     "puter",