Update notebooks with the results of the track

[alex-hse-repository]

🚀 Feature Request

Add info about the forecast decomposition in the notebooks

Proposal

1. In custom_transform_and_model.ipynb

• Fix code for custom models to run without fails
• Add example of implementing the forecast decomposition logic for LightGBM -- it can be done similar to Catboost. See pred_contrib parameter in predict

2. Create notebook forecast_interpretation.ipynb:

• Show how to get forecast decomposition for CatBoost, SARIMA, BATS models and visualize the decomposition
• Show how to get the forecast components into TSDataset
• Show the how to get and plot feature relevance with plot_feature_relevance for both types of relevance table

Test cases

No response

Additional context

No response