add justification of the relation with hyp{o,er}nyms.

Something like

```
semigroup
 * hyponyms (transitive)
    monoid since module monoids includes semigroup
    group since module group includes monoids includes semigroup.
```

this is somewhat like the explanations in flatsearch. BTW, all the "includes" should be clickable and give us the relevant part of the module graph with the path highlighted. 
