Webcomic Keyboard Navigator от jeremy-deutsch

This extension lets you navigate back and forth in a webcomic using your arrow keys!

To use the extension, right-click a "forward" or "back" button on a page of the comic to register it with the extension using the context menu. You can then use the right or left arrow keys, respectively, to navigate the comic, instead of clicking on that button! The extension saves your settings automatically, so you don't have to register those buttons more than once.