There are already many requests for this, but this simply can't be stressed enough - working on "about:*" and new tabs is simply essential, without it the workflow can be very un-smooth. Moreover, please include as many built in commands as possible from Firegestures (view image for example is missing, but very useful), not everyone can write scripts after all.
If you are missing a command, request it on GitHub. Web extensions don't have access to about: and internal pages, and will never be supported unless Mozilla decides to provide access to them.
