Offer to co-maintain Mailchimp

Seeing as 💬 Offering to co-maintain Mailchimp Closed: outdated is already open, I'm happy to either 1) let the process move along that front and close this as won't fix or 2) be added as a maintainer and help w/ transitions from one major drupal version to another.

Hey @heddn! Thanks so much for the offer. We're still on track for a D10-compatible release this week. Given that, I'm going to close this for now, but if we run into the need for more people power on this front, I hope you won't mind if I ping you again.

@bdimaggio Thanks for the release :)