Footnote in AST lacks index information

The `HasFootnote` instance for Pandoc AST ignores the footnote identifiers, and labels:

https://github.com/jgm/commonmark-hs/blob/c9afe7c1ca25dbc1f0580187bb422bd1681ae1b5/commonmark-pandoc/src/Commonmark/Pandoc.hs#L215-L219

And it looks like Pandoc is doing its own state management to compute the identifier, and render the references accordingly. Is storing these footnote identifiers/labels in the Pandoc AST explicitly out of scope?