sourceIndex on selector nodes #36
Description
I just noticed that sourceIndex is undefined on selector nodes. Seems like selectors nodes should get that data just like the other nodes.
A use-case is to get the index of one selector within a selector list: I might parse the selector list .foo .bar .baz, a b, then run selectorListNode.each(selectorNode => {..}) and within that function want to know selectorNode.sourceIndex.
Just a feature idea.