feat: Add HTML/CSS live preview with asset protocol support

[zeelsheladiya]

Pull Request

This PR adds a highly requested feature: Live HTML/CSS Preview directly within the editor. It addresses issue #156 by allowing developers to view rendered HTML files in real-time as they edit, without needing to save the file or open an external browser. Crucially, it solves the problem of relative file paths (like <link href="style.css">) in unsaved buffers by leveraging Tauri's asset protocol.

Description

• New HtmlPreview Component: Implemented a dedicated preview component using an iframe with srcDoc for instant rendering of editor content.
• Asset Protocol Integration: Developed a mechanism to dynamically inject a <base href="..."> tag into the preview's HTML. This points to the file's actual directory on disk using the secure asset:// protocol, ensuring that relative resources (CSS, JS, Images) load correctly.
• Store Updates: Updated buffer-store.ts to include an isHtmlPreview state, allowing the editor to manage HTML preview tabs alongside Markdown and code buffers.
• Toolbar Integration: Added a "Preview" (Eye icon) toggle button to the breadcrumb bar that automatically appears when editing .html or .htm files.
• Live Reloading: The preview updates automatically on every keystroke, providing an immediate feedback loop for frontend development.

Screenshots/Videos

demo.mp4

Related Issues

Closes #156

[mehmetozguldev]

LGTM