Sort References by Order of Appearance in Document

[samm82]

As mentioned in #729, there should be a function that creates an Ordering to be passed into bibMap and citationsFromBibMap to sort the references by order of appearance in the document.

[balacij]

If we want to sort references by order of appearance in documents, it might be simplest to switch to a Stateful renderer. Otherwise, we would need to pre-calculate how things would be rendered (without rendering the artifacts), keeping track of the order citations appear, and then using that ordering in the real deal rendering.

I think we've seen enough issues such that I'm convinced a Stateful renderer wouldn't be a bad thing, necessarily. @JacquesCarette Do you have any thoughts on this?

Some more tickets this where this might be helpful

1. Determine Document Outline from Actual Document Contents #946
2. Printing mdBook SRS to different files / Generating multi-file software artifacts #3796
3. ? (I will update as I go along thru the tickets) MOVED TO Stateful artifact rendering: Verify it makes sense to implement (and implications), design, and implement #3864

[JacquesCarette]

A stateful renderer would not be a bad thing.

I'm not a big fan of having references in order of first appearance - but there are styles that require this. So we should have the capability to do so.