How is the "Used by" button shown on the Repository

I’m not quite sure if this matches for this board, but the others seemed more off so I ask here (If posts can be moved, feel free to move it).

I recently saw on a repository of an API, that it had a “Used by” button on top, right next to the “Watch” button and I was wondering what would be the requirement(s) to make this button display, as I myself have an API publicly available, which is also OS here on GitHub.

Is there any kind of code-requirement, or a setting that has to be enabled in order to activate this?

So this means that only project using maven would be displayed in the dependents page, since my Project is Java based.

Or would that not happen at all due to me using Gradle for dependency-management?