restore tabs with local page por rationex

Mocha Rain Startpage replaces the Firefox home page and new-tab page
with a fully local Catppuccin Mocha-themed interface.

Features:
- Local animated start page
- Search and configurable website shortcuts
- Catppuccin Mocha visual design
- Optional restoration of the most recently closed Firefox window
- No analytics, advertising, telemetry, or remote code

All HTML, CSS, JavaScript, and image assets are included in the
extension package.