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I think you'll have to wait for Mozilla to add Forcetouch support.
As far as I know Forcetouch is open for all who want to use it.
I could, probably likely, be wrong as I have absolutely no evidence to point to 😉

Maybe there's a Forcetouch add-on out there?
 
I've searched for a force touch add on. Doesn't seem to exist. I don't know why Firefox is dragging their feet on this. I've had to make the switch to Safari, which is a drag, but I will continue to do she Safari until Firefox catches up to the technology. Not impressed as its been 6 months now
 
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