Currently we have [Distributed Tracing with Linkerd](https://linkerd.io/2/tasks/distributed-tracing/) which dosen't use the add-on model, but we are seeing more automatic [integrations](https://github.com/linkerd/linkerd2/pull/4177) when it is used! It would be nice to move the existing documentation around the add-on model.