Create index.html for this Repository

# Create `index.html` for OS Repository with CSS and JavaScript

## Description
Develop an `index.html` page to showcase information about supported operating systems for LinuxDroid. The webpage should be styled using an external `style.css` file and include interactivity through a `linuxdroid.js` file. Ensure the page is visually appealing, easy to navigate, and responsive across devices.

## Tasks
- [ ] Create an `index.html` file with a clean and semantic structure.
- [ ] Style the webpage using an external `style.css` file.
- [ ] Add interactivity using the `linuxdroid.js` file (if necessary).
- [ ] Include a navigation bar for easy access to different sections of the OS list.
- [ ] Ensure responsiveness for various screen sizes (desktop, tablet, mobile).
- [ ] Test the page across different browsers to ensure compatibility.

## Notes
- The CSS file (`style.css`) should follow best practices for styling, including mobile-first design.
- JavaScript (`linuxdroid.js`) should be lightweight and optimized for performance.

Issueで説明されているOSショーケース用に、index.html、style.css、linuxdroid.jsを作成してください。まずリポジトリの構成と既存のプロジェクト内容を確認し、その後ナビゲーションとレスポンシブなページを構築してください。デスクトップ、タブレット、モバイルの各ブラウザでページが利用でき、必要に応じて軽量なJavaScriptが使われていれば完了です。

索引モデルが issue の本文から書いたものです。