`linkConnectionPoint(linkView, view, magnet, reference)`

- this function allows you to customize what are the sticky points of links. The function must return a point (with `x`

and `y`

properties) where the link sticks to the element.
The function takes the link view, element view, the magnet (SVG element) the link should stick to and a reference point (either the closest vertex or the sticky point on the other side of the link).
Note that there is a utility function shapePerimeterConnectionPoint that can
be directly passed to the `linkConnectionPoint`

parameter. This function tries to find
the best possible connection point right on the perimeter of the connected shapes. See the function
documentation for details.