Start the Beginners tutorial
The old platform-demos tutorials in gnome-devel-docs should be coalesced into a single set of beginners tutorial and overview of GTK (and possibly other libraries). Instead of having wildly different content, we should merge everything into a singular text, with a consistent voice, and have code examples in different languages.
The beginners tutorial for Python is a fairly good base for that; additionally, we have HowDoI content for some widgets that should find a new home in the tutorial.