Use review scores to create link preview cards for the materials

[hexylena]

[bebatut]

I am lost there :)

[hexylena]

We can use the review scores and announce them in the ld-json of the materials, which some sites may choose to render, e.g.

[hexylena]

the description was not good, but it's also not a newcomer issue (feedback.py probably needs to be rewritten to rewrite output feedback csv into a more structured data format that's easier to access in the metadata.)