- Fixed dark/light theme foreground/background compatibility

- Removed file extension in settings

- Fix overflow issue for long feed urls

- Added custom theme support

- Fixed default variable setting in settings when an option is undefined

- Improved extended feed scan, added this setting in settings page

Extension Functionality Enhancements:
- Implemented new background script functionalities including feed detection, icon state management, and settings initialization.
- Applied theme settings and added a settings button to the popup.
- Added theme and ignored sites management in the settings page.

Code Quality Improvements:
- Switched to webpack infrastructure