v2.0.0

• Re-structure and re-implement the MLP, Metaheuristic-trained MLP, and Gradient Descent-trained MLP models.
• Remove dependency on the Skorch library.
• Add the MhaMlpTuner class, which tunes hyperparameters for Metaheuristic-based MLP models.
• Add the MhaMlpComparator class, which compares multiple Metaheuristic-based MLP models.
• Update examples, tests, and documentation.
• Update requirements, citations, and README.