Draft: window: Use HdyLeaflet for main content
Based on the mockups from Tobias Bernard @ software-mockups: https://gitlab.gnome.org/Teams/Design/software-mockups/-/blob/93095538c8628971a76ce6a36078f155bfc5f31f/adaptive/explore-page.png
Based on the mockups from Tobias Bernard @ software-mockups: https://gitlab.gnome.org/Teams/Design/software-mockups/-/blob/93095538c8628971a76ce6a36078f155bfc5f31f/adaptive/explore-page.png