feat(ci): add GitHub Action for Python tests, fix EarlyStopping logic, and add unit tests

[Bjarten]

This PR introduces several key changes:

1. A GitHub Actions workflow for continuous integration, running tests across multiple Python versions.
2. Fixes to the EarlyStopping class logic, changing best_score to best_val_loss to improve clarity and correctness.
3. A new test suite for the EarlyStopping class to ensure its correct behavior after the logic fix.

Changes:

• Added Python application tests:

  • A new workflow named "Python Application Tests" runs on GitHub Actions.
  • Tests are executed across multiple Python versions (3.9, 3.10, 3.11, 3.12).
  • The workflow is triggered on pushes and pull requests to the main branch.
  • Pip dependencies are cached to optimize performance.

• Fixed EarlyStopping logic:

  • The variable best_score was renamed to best_val_loss for clarity, improving the code's readability and matching the purpose of the variable.
  • Logic for early stopping was updated to properly handle edge cases for delta and stopping conditions based on validation loss behavior.

• Added Unit Tests for EarlyStopping:

  • The file test_early_stopping.py contains a thorough set of tests covering:
    • Initialization and attribute checks.
    • Behavior when validation loss improves.
    • Handling when validation loss does not improve.
    • Proper functionality of patience and delta parameters.
    • Edge cases for early stopping triggers and verbose output.

Why this change is important:

• Automates testing across different Python versions to ensure compatibility and reliability.
• Fixes logic issues in the EarlyStopping class, making it more robust and clear.
• Ensures the EarlyStopping class functions as expected through the added unit tests.
• Improves development velocity by automatically running tests on every push and pull request.