MAINT: Add an empty `__init__.pyi` file to `np.core`
MAINT: Add an empty `__init__.pyi` file to `np.core`

Prevents mypy crashes related to import cycles.

See https://github.com/numpy/numpy/issues/17316

mattip/numpy,anntzer/numpy,endolith/numpy,madphysicist/numpy,seberg/numpy,grlee77/numpy,mattip/numpy,jakirkham/numpy,charris/numpy,pdebuyl/numpy,anntzer/numpy,pdebuyl/numpy,numpy/numpy,seberg/numpy,charris/numpy,simongibbons/numpy,numpy/numpy,mhvk/numpy,mattip/numpy,pbrod/numpy,endolith/numpy,grlee77/numpy,mhvk/numpy,pdebuyl/numpy,rgommers/numpy,mhvk/numpy,grlee77/numpy,simongibbons/numpy,pbrod/numpy,endolith/numpy,mhvk/numpy,madphysicist/numpy,seberg/numpy,simongibbons/numpy,anntzer/numpy,grlee77/numpy,pdebuyl/numpy,numpy/numpy,mattip/numpy,anntzer/numpy,simongibbons/numpy,rgommers/numpy,rgommers/numpy,rgommers/numpy,seberg/numpy,jakirkham/numpy,endolith/numpy,pbrod/numpy,jakirkham/numpy,madphysicist/numpy,pbrod/numpy,mhvk/numpy,jakirkham/numpy,pbrod/numpy,simongibbons/numpy,charris/numpy,madphysicist/numpy,madphysicist/numpy,charris/numpy,numpy/numpy,jakirkham/numpy,grlee77/numpy