text: Title: Add sigmoid_kernel Function
  Body: The sigmoid kernel converts data via tanh into a new space. This is easy difficulty, but requires significant benchmarking to find when
  the scikit-learn-intelex implementation provides better performance. This project will focus on the public API and including the benchmarking 
  results for a seamless, high-performance user experience. Combines with the other kernel projects to a medium time commitment.
  
  Scikit-learn definition can be found at:
  https://scikit-learn.org/stable/modules/generated/sklearn.metrics.pairwise.sigmoid_kernel.html
  
  The onedal interface can be found at:
  https://github.com/uxlfoundation/scikit-learn-intelex/blob/main/onedal/primitives/kernel_functions.py#L127