The `'connectionLength'` link anchor function places the anchor of the link at a point a specified length along reference link (counting from reference link's source). It accepts one argument, which can be passed within the `linkAnchor.args` property:

length | number | The length at which to place the target anchor. Default is `20`, meaning a point 20 pixels from the source of the reference link.

Example:

    link.source(link2, {
        linkAnchor: {
            name: 'connectionLength',
            args: {
                ratio: 50
            }
        }
    });