Whether you're wanting to get started with developing Vortex extensions or you just want to speed up the process of creating new Vortex extensions, you might be interested in my new package: create-vortex-extension.
You don't actually need to install anything to use it. Assuming you have a recent version of npm installed, just run npm init vortex-extension and it will be automatically downloaded. Just answer the questions and everything you need to get started with an extension (ready-to-run!) will be created in the current directory.