docs: enhance ML library descriptions with additional context

[AsadUllah428]

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[JinyangWang27]

@AsadUllah428 Thanks for your contribution. The addiitons to the first two entries are great.
However, I tend to not agree with the modification for xgboost, for the following reasons:

1. it's not a general ML library
2. gradient boosting already implies ML
   Could you please remove the modification to xgboost? Then it's ready to be merged.