Messenger 4 customizability

Recently we launched a new version of our Messenger. Among other big changes like an introduction of a home screen and apps, we also introduced more customizability options that allow businesses to use a 2-color scheme and use their logo. It's been great seeing them in the wild.

It's been a massive team effort, thanks to @Matt Yow, @Justin Pervorse, @Coby Chapple and @Paul Murphy and the rest of the team.