The release notes of WhatsApp Messenger 2.18.20 they only talk about bug fixes, but the new version of the messenger does come with a good news: support for CarPlay, as informed by the iCulture (Google translator).
Before, WhatsApp already had its integration with Siri using the framework SiriKit. Since the launch of iOS 10, users can send messages through the service talking to Siri. Now, however, Facebook (owner of WhatsApp) has expanded this integration a bit, placing a icon in Apple's automotive media center.
The application, however, is very limited. You can not open it and walk through the various conversations, for example. Everything that happens when you touch the icon on CarPlay opens a new conversation so that you can dictate the content and send it to the person you want. In addition, messenger notifications appear on CarPlay, and you can tap them to listen to and respond to them.
Of course, it would be much more interesting if the app for CarPlay were able to do more things, however, this apparently does not depend so much on Facebook but on the API that Apple releases for developers. Still, we're talking about the first third-party messenger (that is, not counting Apple's Messages) available for CarPlay.
Unfortunately, here in Brazil, CarPlay has not yet shown what came mainly because Apple has not yet made available its own map solution on it. And since there is neither Waze nor Google Maps (nor any other map) available, it ends up becoming very limited.