Adding cannon's lock constraint

src/Physics/Plugins/babylon.cannonJSPlugin.ts

@@ -186,6 +186,9 @@
                         localAnchorB: constraintData.pivotB
                     });
                     break;
+                case PhysicsJoint.LockJoint:
+                    constraint = new CANNON.LockConstraint(mainBody, connectedBody, constraintData);
+                    break;
                 case PhysicsJoint.PointToPointJoint:
                 case PhysicsJoint.BallAndSocketJoint:
                 default:

src/Physics/babylon.physicsJoint.ts

@@ -69,6 +69,7 @@ module BABYLON {
         public static PointToPointJoint = 8;
         //Cannon only at the moment
         public static SpringJoint = 9;
+        public static LockJoint = 10;
     }
 
     /**