Allow tag researching

[ZynoXelek]

Would be nice to have the possibility to search articles by their tags, similarly to this site for instance : https://mizu.re/

[ctmbl]

I'd precise, we want to display the list of tags in a side panel (maybe in the left menu).
currently such a list exists at https://iscsc.fr/tags but no link goes there.

We could even add such a list or link to this list on the 404 page