Show datasets in the element details panel

Closes #1294 (closed)

I created a new Pinia store for elements and migrated the Details Panel component to TypeScript, so it will be easier to go on without much debt.

This implementation handles the pagination, but it would be much better to either:

• Use non paginated endpoints for such a case
• Use a generic way to paginate those results in the frontend (I'm not sure how to do that properly in JS)