Publishing a new release 4.0.0

[larsolofsson]

I have created a draft of the release document
https://github.com/papinet/papiNet-API/releases/edit/untagged-96a1121351f113a94f50

How to create following files and the heading Assets in the release document?
Assets 2
Source code m (zip)
Source code (tar.gz)

Is it added automatically when publishing the release?