Specify include_package_data to setup

[vyasr]

Description

For pure setuptools-based builds, the include_package_data option historically defaulted to False. With newer projects, i.e. with projects containing a pyproject.toml file, it defaults to True. However, for projects using scikit-build this setting must be provided explicitly to the setup function (not in the config file) to allow scikit-build to intercept the argument and use it in the preprocessing it does before invoking setuptools.setup.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[jakirkham]

/merge

[bdice]

I confirmed: conda packages now contain the pxd files.