[Sankey] edge width and node align

### What problem does this feature solve?
1、Edge width
Now edge width is determined by the value of links。But when there is only one node in each layer，and the value of links is not different，start width of the edge is inconsistent with the source height。I hope this problem can be corrected in the future。
As shown below：
As mark 1 in the picture。
2、Nodes
（1）Nodes align：Can you increase the top or bottom alignment of the nodes?
（2）Nodes height: When a node has a branch, the height of the node will be equal to the sum of the branch heights, resulting in the height of the node being greater than its parent node.As mark 2 in the picture。

中文版本：
1、边的宽度
当前边的宽度由links中的value决定，这样当每一层都只有一个节点并且links中value值不同时，会导致边的起始位置的宽度始终会小于source节点的高度。如图中1处，边起始的宽度就和source节点的高度不一致。
2、节点
（1）节点对齐：能否增加节点的顶部或者底部对齐？
（2）节点的高度：当一个节点有子节点时，其高度等于子节点的高度之和，导致该节点的高度超过了其父节点的高度。如图中2处节点的高度，明显大于其父节点的高度。

### What does the proposed API look like?
希望可以解决上述问题