title: Google maps flutter zoom in/zoom out
body: <p>I am trying to create a sample app like Uber with google_maps_flutter: ^0.5.10 .. In Uber app when you select a pickup/drop location, and you do double tap (to zoom in) or zoom in/zoom out scaling the screen it always happens respective to the center of screen. Whereas when I add the google maps in flutter and if I do double tap lets say on right bottom of screen, google maps zoom and takes the view to the area where it was tapped. Similarly it happens with the scaling (pinching screen). The area I scale the camera view goes to that particular location. But I want double tap or scaling to stay centered to my selected location (like in Uber). </p>
  
  <p>I did achieve it using cameraMove and cameraStop callbacks. In that I determine if camera was moved due to a zoom, I get the last zoom factor and move camera back to my selected location with the new zoom factor. It works but does not looks good if I double tap on left corner the camera goes back to original position. Similarly I did for the scaling zoom as well to zoom in/zoom out the camera moves back to original location I selected. </p>
  
  <p>Then I tried GestureDetector on top of the GoogleMaps. Inside that I handled the onDoubleTap. That looks neat as I just change the zoom factor on double tap and keep location same. But I am not able to achieve scaling zoom in/out using onScaleUpdate (etc) functions on GestureDetector. </p>
  
  <p>Is there any better way in Google maps flutter plugin to do all this?</p>