Introduces a full browser customization system with support for theme presets, live editing, import/export, and non-destructive design. Adds new documentation for customization, updates the features list, and implements a ThemeManager for loading and managing themes at the application level. Updates home and settings pages to support live theming and preview, and adds four built-in themes (default, forest, ocean, sunset).
Added detailed documentation files for code of conduct, contributing guidelines, core concepts, features, and project structure in the documentation/ directory. Updated README.md to reference new documentation, expand feature descriptions, and clarify setup instructions.
andrew