Add documentation tabs for datasets, models and metrics

[tejasstanley]

This PR adds separate documentation tabs for datasets, models, and metrics in the PerceptionMetrics documentation.

Changes

• Adds a dedicated datasets documentation page explaining the available dataset adapters and their expected usage.
• Adds a dedicated models documentation page explaining the available model wrappers and how they connect external models to PerceptionMetrics.
• Adds a dedicated metrics documentation page explaining the segmentation metrics reported by PerceptionMetrics, including precision, recall, accuracy, F1-score, IoU, Dice score, and macro/micro averaging.
• Updates the documentation navigation to include the new datasets, models, and metrics pages.

Reference Issue : #595