Static node offset

[joao-m-santos]

Feature description

Allow for setting an offset property in each alluvial node (dataset) that forces the offset value between said node and its previous node (previous in its column).

This property would overwrite the d3-sankey nodePadding option for only the nodes that have it.

Problem/motivation

In order to avoid confusing link overlaps, there are cases where it's better to set a hard offset distance between nodes.

Describe alternatives you've considered

• Fork d3-sankey and rewrite the collision methods - too much effort and not sustainable

Additional context

This is useful together with custom curve functions.

Validations

• [X] Follow our Code of Conduct
• [X] Read the Contributing Guidelines.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.