CLI around Astal to scaffold and run projects. Astal is a set of libraries written in Vala/C that makes writing a Desktop Shell easy. It also has an accompanying JavaScript library which lets you write Desktop Shells in JSX running on GJS. GJS is a JavaScript runtime built on Firefox's SpiderMonkey JavaScript engine and the GNOME platform libraries, the same runtime GNOME Shell runs on.
To get started read the wiki.
Note
Wiki of the legacy v1 is still available on aylur.github.io/ags-docs/.