With Solar systems, you do all your work in a "Vendor" namespace. All
libraries, apps, models, and other files that you write will be placed in your
vendor tree. You can choose your own vendor name; for these examples, we will
use a vendor namespace called Example.
To make the Vendor tree in your Solar system, go to the project root at the
command line and call the make-vendor command:
$ ./script/solar make-vendor Example
This will create source directories your apps, fallback view helpers, and so on. It will also set up symbolic links for the include directory and public assets.