skpkg: Add requirements to the folder

[stevenhua0320]

@sbillinge Ready for review

• Fix correct import of tifffile,
• Fix correct import of _configPropertyR,
  now the pytest is shown below

pytest
===================================================================== test session starts ======================================================================
platform darwin -- Python 3.13.9, pytest-8.4.2, pluggy-1.6.0
rootdir: /Users/huarundong/dbs/diffpy.srxplanar/diffpy.srxplanar
configfile: pyproject.toml
plugins: env-1.2.0, cov-7.0.0
collected 1 item                                                                                                                                               

tests/test_version.py .                                                                                                                                  [100%]

======================================================================= warnings summary =======================================================================
src/diffpy/__init__.py:16
  /Users/huarundong/dbs/diffpy.srxplanar/diffpy.srxplanar/src/diffpy/__init__.py:16: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
    __import__("pkg_resources").declare_namespace(__name__)

src/diffpy/__init__.py:16
  /Users/huarundong/dbs/diffpy.srxplanar/diffpy.srxplanar/src/diffpy/__init__.py:16: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('diffpy')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    __import__("pkg_resources").declare_namespace(__name__)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
================================================================ 1 passed, 2 warnings in 0.72s =================================================================```