Nissan: allow B drive mode for Nissan Leaf (#29228)

* CAR.LEAF: NissanCarInfo("Nissan Leaf 2018-22”), video_link= "https://youtu.be/vaMbtAh_0cY&t=0s"),

Add Youtube video 2019 Leaf

* Update selfdrive/car/nissan/values.py

* Update interface.py

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Co-authored-by: Shane Smiskol <shane@smiskol.com>
old-commit-hash: b50ffc4360

selfdrive/car/nissan/interface.py

@@ -47,7 +47,7 @@ class CarInterface(CarInterfaceBase):
     be.type = car.CarState.ButtonEvent.Type.accelCruise
     buttonEvents.append(be)
 
-    events = self.create_common_events(ret)
+    events = self.create_common_events(ret, extra_gears=[car.CarState.GearShifter.brake])
 
     if self.CS.lkas_enabled:
       events.add(car.CarEvent.EventName.invalidLkasSetting)