Training Code - v1.0.0

Add new training code (training-code.ipynb) with improvements over v1:

- Enhanced dataset handling with `SpriteDataset` class for dynamic frame dimension grouping.
- Implemented separate `DataLoader` instances for each frame size to ensure dimension consistency.
- Introduced `PixelArtLoss` combining MSE, alpha, and color consistency for better pixel art quality.
- Upgraded `Animator2D` model with `TextEncoder` (T5-based) and `FrameGenerator` for metadata-driven frame generation.
- Added comprehensive training loop with progress bars, checkpoint saving, and visualization (PNG/GIF outputs).
- Improved error handling and logging for dataset validation and frame processing.