Extend bbox x or y

Allow for extending or reducing bounding boxes in x and/or y direction

Complementh this to `CameraConfig`

```python
def rotate_transform_bbox(self, angle, xoff, yoff, x_add, y_add):
    """
    ...
    x_add: float, optional
        Addition distance in x-direction [m]
    y_add: float, optional
        Addition distance in y-direction [m]
    ...

    """
```