[w3c/gamepad] GamepadHapticActuator pulse should be annotated [Throws, NewObject] (#59)

In the spec of [pulse](https://w3c.github.io/gamepad/extensions.html#dom-gamepadhapticactuator-pulse()), it didn't describe how the detailed of this interface to be implemented. We should make implementers know we can't throw `Promise` without `Throws`, and it needs to return a `NewObject` always to avoid making users confusing to get a nullptr. 

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