[Feature request] Add reverse Blendshape sync

[blufish1234]

I think it would be great if there is such a script that can set a blendshape's value to 0 when the controller blendshape has a value of 100, and back to its original value when the controller blendshape goes back to 0. It would be in good use in situations such as certain eye morph options may make blinking strange, so resetting these to 0 would make them normal again, and back to normal values when not blinking.

[Sayamame-beans]

Related #396 , #503 ?