W&B Logger Documentation updates

[digantamisra98]

Minor documentation changes for W&B logger in gitbook. Requesting edit access to the demo colab notebook to showcase the functionalities for W&B.

[coveralls]

Pull Request Test Coverage Report for Build 716039297

• 24 of 25 (96.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 76.039%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
avalanche/evaluation/metrics/forgetting.py	0	1	0.0%

Totals
Change from base Build 709483130:	0.08%
Covered Lines:	6493
Relevant Lines:	8539

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💛 - Coveralls

[AndreaCossu]

Thank you @digantamisra98. Currently, the From Zero to Hero tutorial is updated through the notebooks you see in the notebooks folder. Can you modify that notebook instead of directly the gitbook? Also, the colab notebooks will be kept in sync automatically once you modified the notebook here on avalanche. See #482

[digantamisra98]

@AndreaCossu for the colab notebooks, I believe I will have to run them and save the cell output as well so it would make sense if I run them on a W&B Teams account for Continual AI, which would serve as the central dashboard.