docs: add setup guide

.vitepress/config.mts

@@ -37,11 +37,11 @@ export default defineConfig({
           text: 'Docs',
           items: [
             {text: 'Getting Started', link: '/getting-started'},
+            {text: 'Setup', link: '/setup'},
             {text: 'Process Promise', link: '/process-promise'},
             {text: 'API Reference', link: '/api'},
             {text: 'Configuration', link: '/configuration'},
             {text: 'CLI Usage', link: '/cli'},
-            {text: 'Package', link: '/package'},
             {text: 'Migration from v7', link: '/migration-from-v7'},
           ],
         },

package.md → setup.md

@@ -1,6 +1,49 @@
-# Package
+# Setup
 
-## Hybrid
+## Requirements
+* JavaScript Runtime:
+  * Node.js 12.20.0 or later
+  * Bun 1.0.0 or later
+* Some kind of bash or PowerShell
+
+## Install
+
+::: code-group
+
+```bash [node]
+npm install zx
+```
+
+```bash [bun]
+bun install zx
+```
+
+```bash [deno]
+deno install -A npm:zx
+```
+
+```bash [brew]
+brew install zx
+```
+
+:::
+
+## Bash
+
+zx mostly relies on bash, so make sure it's available in your environment. If you're on Windows, consider using [Windows Subsystem for Linux](https://docs.microsoft.com/en-us/windows/wsl/install) or [Git Bash](https://git-scm.com/downloads).
+By default, zx uses bash, but you can switch to PowerShell by invoking `usePowerShell()` or `usePwsh()`.
+
+```js
+import { useBash, usePowerShell, usePwsh } from 'zx'
+
+usePowerShell() // Uses PowerShell.exe
+usePwsh()       // Looks for pwsh binary (PowerShell v7+)
+useBash()       // Switches back to bash
+```
+
+## Package
+
+### Hybrid
 zx is distributed as a [hybrid package](https://2ality.com/2019/10/hybrid-npm-packages.html): it provides both CJS an ESM entry points.
 
 ```js
@@ -20,15 +63,15 @@ const opts: Options = {
 }
 ```
 
-## Bundled
+### Bundled
 
 We use [esbuild](https://dev.to/antongolub/how-and-why-do-we-bundle-zx-1ca6) to produce a static build that allows us to solve several issues at once:
 * Reduce the pkg size and install time.
 * Make npx (yarn dlx / bunx) invocations reproducible.
 * Provide support for wide range of Node.js versions: from 12 to 22.
 * Make auditing easier: complete code in one place.
 
-## Composite
+### Composite
 
 zx exports several entry points adapted for different use cases:
 * `zx` – the main entry point, provides all the features.