docs: tutorial on new features for score-based methods #1392 (#1489)

* tutorial on new features for score-based methods + index on website

* modif for review

* modif for review

* modif for review

* change graphical labels

* change graphical labels

* syntax corrections

* last display modif

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Co-authored-by: Camille Touron <ctouron@ptb-07008323.grenoble.inria.fr>

Author: touronc