Feature request: ability to highlight new contributors

[jedevc]

Is your feature request related to a problem? Please describe.
As a maintainer, I want to highlight the work that new contributors do, and be able to call them out at the bottom of release notes. I remember getting started in open source, and getting that call out was a huge motivator to keep going 💛

Describe the solution you'd like
I'd love a way to somehow work out which contributors are new in a given release. I don't think there's a way to do this?

I'd be able to get it to work, if there was a way to get information about previous releases, and be able to iterate through them? Something like BatchData.PreviousReleases, I guess as an enhancement of #224?

Describe alternatives you've considered
Not really, any alternatives, aside from adding a custom generation step / manual editing step, which I kinda want to avoid.

Additional context
Nope!

[miniscruff]

https://github.com/dbt-labs/dbt-core/blob/main/.changie.yaml

This is how dbt does it.