Add record fields to imenu output

Is there a reason that record fields are not available in imenu? If not it seems like it might be a good idea to add them.

Start by locating the Emacs Lisp code that builds imenu output and inspect how Haskell declarations are currently represented there. Determine how record fields should appear alongside existing entries; done means record fields are included in imenu output and the behavior is covered by the relevant tests, if present.

Written by the indexing model from the issue text.