feat(SmartDataDbDoc): add static .getCount({}) method

test/test.ts

@@ -199,12 +199,18 @@ tap.test('should store a new Truck', async () => {
   const truck = new Truck('blue', 'MAN');
   await truck.save();
   const myTruck2 = await Truck.getInstance({ color: 'blue' });
+  expect(myTruck2.color).toEqual('blue');
   myTruck2.color = 'red';
   await myTruck2.save();
   const myTruck3 = await Truck.getInstance({ color: 'blue' });
-  console.log(myTruck3);
+  expect(myTruck3).toBeNull();
 });
 
+tap.test('should return a count', async () => {
+  const truckCount = await Truck.getCount();
+  expect(truckCount).toEqual(1);
+})
+
 tap.test('should use a cursor', async () => {
   const cursor = await Car.getCursor({});
   let counter = 0;