Fix camera looking back to the origin after calling move_camera() (#…

…3920)

This PR fixes a problem introduced by PR #3544: The camera kept looking
at the origin when calling `move_camera()` with given `look_at_*`
coordinates.

The fix can be verified with the following snippet. Moving back and
forth between the spheres should not point the camera back to the
origin, an the orbit controls should orbit around the sphere which is
currently looked at:
```py
with ui.scene() as scene:
    scene.sphere().move(1, 2, 0).material('blue')
    scene.sphere().move(4, 5, 0).material('red')

ui.button('blue', on_click=lambda: scene.move_camera(*(1, 2, 3), *(1, 2, 0), *(0, 1, 0), duration=1))
ui.button('red', on_click=lambda: scene.move_camera(*(4, 5, 6), *(4, 5, 0), *(0, 1, 0), duration=0))
```

nicegui/elements/scene.js

@@ -452,6 +452,8 @@ export default {
           if (camera_up_changed) {
             this.controls.dispose();
             this.controls = new OrbitControls(this.camera, this.renderer.domElement);
+            this.controls.target.copy(this.look_at);
+            this.camera.lookAt(this.look_at);
           }
         })
         .start();