If components should be external, provide a mechanism to publicize them
What
There should be a listing of components from external contributors. This might come with a caveat that these are not developed or supported by the core team.
Why
This provides a way to connect your users with your external contributors, which encourages both groups to be more involved with your software ecosystem.
When
Once you are aware of external contributions
In some cases, teams prefer to that contributions remain external to the core library. This is often to reduce the maintenance burden on the core team, or to prevent dependency bloat. So external contributions are instead treated as plugins or kits that build on the core library.
While that’s a perfectly reasonable decision to make, the problem is that you now have no way to connect your users with the external contributions. Creating such a mechanism is both a way to help your users and to reward the efforts of external contributors, thus encouraging more contributions.