Retaining comments

[Nemo157]

I'm undecided whether this is worthwhile, but the AST could have nodes added to retain comments when parsing extended diagnostic notation. These could then be included when outputting either diagnostic notation, or as part of the annotated hex output.

This wouldn't really help with what I see as the main usecases though, converting EDN -> bytes for tooling that wants human writeable input, or converting bytes -> {EDN, annotated hex} for tooling that wants to show human readable output.