Adds support for eBay results lists that can be found via the category or browse sections, rather than strictly search results.

- Firefox support
- Now uses MutationObservers to modify the page as it loads, rather than waiting for the page to load then modifying it. Results in a much smoother experience
- Localisation support
- New logo, because the Chrome web store wouldn't let me submit without one
- Removed the unneeded 'ActiveTab' permission