markAvailable - marks all the available magnets or elements when a link is dragged (being reconnected). Default is
false. This gives a hint to the user to what other elements/ports this link can be connected.
What magnets/cells are available is determined by the
Internally, available magnets (SVG elements) are given the
'available-magnet' class name and all the available cells the
'available-cell' class name. This allows you to change the
styling of the highlight effect.