I'm reading the documentation for custom packages and there is a specific layout for a package (https://docs.unity3d.com/Manual/cus-layout.html) that is different from Unity project layout. Is there a way to make a Unity project work as a package? I have a project that artists are working on models and animations. I want to import this project to another project in Unity where the game is actually made. I thought that packages would be the correct solution, but seems that packages are different than Unity projects. Can I open a package just like I open a Unity project to edit and then publish to the package manager? Or do I have to copy the files to a package structure and then publish it?