Allow grouping of widgets within category

[ajdapretnar]

Perhaps a silly idea. How about allowing groups within a category?
Use case: in Text add-on, we have a large collection of widgets. I'd like to organize them a bit, for example:

• Text:
  • Data
    • Corpus
    • Guardian
    • Wikipedia
  • Vectorization
    • Bag of Words
    • Document Embedding
  • Ontologies
    • Ontology
    • Word List

Kind of like folders. Would help keep things neat. But this is up for discussion, of course.