[NEW FEATURE] Add train/test split function

[jeipollack]

Problem Description
WaveDiff assumes data has already been split into train and test datasets. We need to modify API to include train/test split functionality to do this for end-users

Proposed Solution
Just add a train-test split function that accepts input dataset and ratio

Alternatives Considered
N/A

Additional Context
N/A

Your insights and suggestions are highly valuable as we consider enhancing our project. Thank you for taking the time to contribute! 🚀