[Feature] support customized chart by custom-mark

[xile611]

What problem does this feature solve?

https://flowingdata.com/projects/2019/relationship-stages/index-pivoted.html?initialWidth=670&childId=stages&parentTitle=The%20Stages%20of%20Relationships%2C%20Distributed%20%7C%20FlowingData&parentUrl=https%3A%2F%2Fflowingdata.com%2F2019%2F03%2F26%2Frelationship-stages%2F

What does the proposed API look like?

{
   type: 'customized',
   ....
}