scope question: add changelog parsing code?

[ericphanson]

I've written some code to parse markdown changelogs, using CommonMark.jl and MarkdownAST.jl. I am thinking about using this potentially for:

• with a REPL mode, being able to query installed packages changelogs (if they have one under some well-known names like NEWS or CHANGELOG.md, and if it's parsable)
• potentially in RegistryCI.jl to allow relaxing the must-have-release-notes-for-breaking-changes-check where one would not need to supply Registrator with the notes if RegistryCI can parse out breaking changes from a changelog in a well-known place
• potentially surfacing changes for CompatHelper, a la @IanButterworth's comment here

This changelog-parsing code could live in a separate package or could be added here. If it were added here, it would add some dependencies:

• CommonMark, for parsing changelogs from files
• MarkdownAST, since my parsing code is based on MarkdownAST's representation
• Dates, for parsing dates
• AbstractTrees, for traversing MarkdownAST trees (already a dep of MarkdownAST)
• and OrderedCollections, since I use an OrderedDict, though this could be dropped if necessary for some other representation (vector of pairs or similar)

It would also add some complexity (currently ~300 LoC, though ~1/3 of that is just the contents of this PR).

Alternatively, it could be a separate package (ChangelogParser.jl or maybe KeepAChangelog.jl or something like that).

Thoughts? cc @mortenpi @fredrikekre

[fredrikekre]

I vote for including it here!