How to set 1 directory from a project in composer?

Question

Composer

Good afternoon, I don’t even know how to formulate it correctly, I ran into a problem:

There is a project, it contains documentation, etc., and the kernel is a separate directory (but this is all 1 repository):

/docs
/test
/core (при установке через composer нужна только эта директория)

How to set up this behavior?
for example, Yii2 does this