Your extension module should be named _hello (notice the leading "_").
pyproject.toml:
# ...
[tool.setuptools]
ext-modules = [
{ name = "_hello", sources = ["src/hc/hello.c", "src/hc/hello.i"] }
]
Check:
[SO]: c program SWIG to python gives 'ImportError: dynamic module does not define init function' (@CristiFati's answer) contains the SWIG related details
[SO]: How to solve Python-C-API error "This is an issue with the package mentioned above, not pip."? (@CristiFati's answer) contains info about building with SetupTools