Special styles for Test/Undo buttons in disabled mode
Add ability to open settings menu from keyboard
(extensions.handyclicks.key.showSettingsPopup preference)
Based on code from Right Links:
https://github.com/Infocatcher/Right_Links/blob/bf85b8f027b58c74afc78eb0157a2cae7881aa3c/chrome/content/rightlinks.js#L1073-L1097