Add button with appmenu (like GNOME Web / Google Chrome) and hide the default "Firefox" button.
Use left click to open appmenu and middle click to open new tab.
Please visit extension's page on addons.mozilla.org for install latest stable version. Also, it is good place for you positive reviews. For post bug reports and feature requests please use issues page. I read it more often. Code of unstable version is contained in next branch. Use it for testing only.