Add table on respec with vocab usage

[nissimsan]

The main thing I'm after is pretty simple - a third pie/bar chart (or just a table) which tell me:

There is a total of 2000 terms defined on this repo

• 900 of them are referencing https://schema.org/
• 700 of them are referencing https://service.unece.org/
• 500 of them are referencing https://w3id.org/traceability
• 100 of them are referencing https://voc.gs1.org/

This could be listed together with the visualizations:
https://w3c-ccg.github.io/traceability-vocab/#ontology-visualizations