Forward-Backward Bookmarks

USAGE: Click the left arrow to go to the previous or the right arrow to go to the next sibling of the current bookmark. WARNING: It searches for the URL. If there were some bookmarks at different directory or different name and the URL was the same it always gives you the first one. It only moves in the folder, I thought I will get lost so I didn't implemented it. REASON: As my bookmarks have grown the depth(folders) have also grown. All I wanted was go to the next bookmark but when I click the bookmark icon the depth was awaited. It was so tedious therefore I created this extension.