Settings > Reading: add a connection to the home template for block themes

[annezazu]

Right now, when you're using a block theme, there's not a clear connection between the Settings > Reading screen and editing the template powering your homepage. Because this connection isn't there, I've seen users note that they aren't sure where to make changes or how changes made to Settings > Reading impact what's in their template. To help make a connection between the two and to encourage folks to edit visually, I think we need to explore a way to connect the experiences. This definitely needs design thinking that I don't have but opening this to start the conversation.