Hn tags hierarchy is not optimized on front page

[ttoine]

Currently, the subtitle of an article is in H4. Considering that the tile of an article is in H2, the subtitle should be an H3 for a better optimisation.

Maybe this is because it uses a specific style, let's see if it's possible to change the HTML to H3, and look what needs to be improved in the CSS if needed

[matks]

Still to do

Subtitle are H4 not H3