Pre-create extensions folder

[George]

If you just build a custom extension and publish it to npm for easy installation, all the required folders will be auto created during installation, see:

Wappler Extensibility - Build Custom Wappler Extensions

The next level of Wappler extensibility - App Connect for our front-end framework is here! Building custom App Connect custom components with their own dynamic attributes, events and data sources is now possible. You can write your own custom components and also provide a UI definition of your extensions so they integrate directly visually in Wappler! You also build custom Server Connect extensions now for the backend. Both type of extensions are described here. Your extensions can be publi…