Add: mouseover with dataset description in table overview

Description of the issue

Currently only table names and tags are shown in the list of tables. The titles sometimes do not help users who look for data to already derive what may be behind that table.

We may want to discuss again, what the typical target group is. Is it mainly those who deposit data and want to link to it, or do we also cater to persons that come to the OEP to find data?

Ideas of solution

• It may be easier for them if a mouseover showed the description of that tables content derived from the metadata field "description" or
• Add a column with the info from metadata field "description" (this may take too much space however)

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md