Options for configuring markers for annotations.
An example of the arrow marker:
{
arrow: {
id: 'arrow',
tagName: 'marker',
refY: 5,
refX: 5,
markerWidth: 10,
markerHeight: 10,
children: [{
tagName: 'path',
attrs: {
d: 'M 0 0 L 10 5 L 0 10 Z',
'stroke-width': 0
}
}]
}
}