CheckThemAll wót Salvatore Meschini

I updated to Firefox 57 and I was looking for a WebExtension replacement for CheckFox, since I was not able to find one, I implemented it. CheckThemAll allows you to select many checkboxes and then check / uncheck / invert them with one single click!

Instructions:

1) Select an area of your page containing the checkboxes you want to check/uncheck/invert
2) Right-click and use one of the features available in CheckThemAll

Note: expand the selection to include the "first" checkbox