Add filter by project dependencies (ecosystem)

IMHO ecosystem should rather be used for modules that can be listed as "Compatible with" whereas "Depends on" should be a new separate entity reference. It shouldn't be a taxonomy like the Ecosystem feature is, but a direct relationship to the module(s) it is dependent upon.

Ideally, this would be:

* populated and synced automatically with dependency data in the modules primary *.info.yml (ie, do not recurse into submodules).
* only (optionally) exposed in the UI to people with an elevated admin role (so as to avoid interference with the aforementioned sync).

Dependencies is very useful idea.
Like the most popular module is ctools in the project browser. But how to use it exactly? I know Panels used it back in the day, but ctools remains a mysterious module to me without knowing the dependents. It would be very helpful to see what modules implements it in order to discover tons of examples of how it can actually be used. Maybe it is useful since being so popular? Maybe it saves time? It would be even more useful for new site builders, whom this module can be extra confusing.

Dependency tree of themes is also needed.
For example, what sub-themes depend on barrio → ?
drupal.org search does not return any results... If there are no sub-themes, there has to be for a site builder.
Having sub-themes easy-to-find might encourage people to submit new sub-themes, and branching out barrio with more advanced sub-themes could provide better user experience.