docs(llms): generate llms.txt from content

[farnabaz]

🔗 Linked issue

nuxt-ui-pro/docs#130

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The LLMs text can be found at https://238e71e9.ui-6q2.pages.dev/llms.txt

Within PR I created a simple module that receives options and generates llms.txt accordingly.

---

Update: we can separate contents into different section via filters

# Nuxt UI v3

> A comprehensive, Nuxt-integrated UI library providing a rich set of fully-styled, accessible and highly customizable components for building modern web applications.

## Getting Started

- [Installation](https://ui3.nuxt.dev/getting-started/installation/nuxt): Learn how to install and configure Nuxt UI in your Nuxt application.
...

## Components

- [App](https://ui3.nuxt.dev/components/app): Wraps your app to provide global configurations and more.
- [Accordion](https://ui3.nuxt.dev/components/accordion): A stacked set of collapsible panels.
-....

## Composables

- [defineShortcuts](https://ui3.nuxt.dev/composables/define-shortcuts): A composable to define keyboard shortcuts in your app.
...

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@3246

commit: 9ef82c9

[cloudflare-workers-and-pages]

Deploying ui3 with    Cloudflare Pages

Latest commit:	9ef82c9
Status:	✅  Deploy successful!
Preview URL:	https://8af837f0.ui-6q2.pages.dev
Branch Preview URL:	https://feat-llms.ui-6q2.pages.dev

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