We just released SearchMage WebExtension that provides infinite scrolling for popular search engines, search result filtering, custom CSS support, dark themes, improved navigation elements for Google, keyboard shortcuts and much more.For Firefox:
https://addons.mozilla.org/firefox/addon/searchmage-search-e...
For Chrome/Vivaldi:
https://chrome.google.com/webstore/detail/searchmage/oldjnha...
Feedback and improvement ideas are welcome.