Show thumbnails of exemplar annotations next to tag selector

[geoffroy-noel-ddh]

Show an illustrative thumbnail of a graph next to each tag in the tag list on the search page.

Purpose: so it is clear for the editor what they represent.

The thumb could be picked randomly among graphs which have been assigned that tag.

Or we could select a a thumb with the 'm.exemplar' tag.

[geoffroy-noel-ddh]

Hi @simonastoyanova , a sample annotation will be shown when you hover a tag in the search page.

The sample is selected among all the annotations tagged with that particular tag.

The selection process works like this:

1. first return an annotation tagged with m.exemplar (and your hovered tag) for the selected allograph
2. if not found, return an annotation (with your hovered tag) for the selected allograph (if any is selected in the facet)
3. if not found, return an annotation with m.exemplar (and your hovered tag)
4. if not found return any annotation with the tag you are hovering