Fire 'GamePad Trigger Pull' once when it goes below activation threshold

[luttje]

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As seen in this discussion, the trigger is only called when it's larger than the threshold. This will cause a connected GamePad Stick action to leave the stick hanging:

Originally posted by @luttje in https://github.com/luttje/Key2Joy/discussions/58

Triggers like this should fire once when they go below the activation threshold, so an action can nicely reset