Packages created on the CI are missing cpp and cuda extension files

[dacorvo]

When building a package locally, the .h, .cpp and .cu files are added to MANIFEST.in automatically by setuptools_scm.

However, when building the package on the CI, or when installing it implicitly from a temporary package (pip install .), the files are not included.

The workaround is to install the package in editable mode on the CI (pip install -e).