Add changelog entry

docs/source/changelog.md

@@ -12,6 +12,42 @@ changes in pull requests], this list should be updated.
 [development releases]: https://hub.jupyter.org/helm-chart/#development-releases-jupyterhub
 [breaking changes in pull requests]: https://github.com/jupyterhub/zero-to-jupyterhub-k8s/pulls?q=is%3Apr+is%3Aclosed+label%3Abreaking
 
+### Default image registry moved to [quay.io](https://quay.io)
+
+We have moved the registry where we publish our docker images from [dockerhub](https://hub.docker.com)
+to [quay.io](https://quay.io). This move is to ensure our users are not [throttled by dockerhub](https://docs.docker.com/docker-hub/download-rate-limit/),
+and us maintainers don't have to apply for 'sponsored OSS Project' from docker each year. This
+should have no material impact on your experience.
+
+For the benefit of people running older versions of z2jh and are throttled by DockerHub,
+we have actually copied all our *released* images from dockerhub to quay.io as well.
+So you can opt in to using the images from quay.io with the following config:
+
+```yaml
+hub:
+  image:
+    name: quay.io/jupyterhub/k8s-hub
+proxy:
+  chp:
+    image:
+      name: quay.io/jupyterhub/configurable-http-proxy
+  secretSync:
+    image:
+        name: quay.io/jupyterhub/k8s-secret-sync
+singleuser:
+  networkTools:
+    image:
+      name: quay.io/jupyterhub/k8s-network-tools
+prePuller:
+  hook:
+    image:
+      name: quay.io/jupyterhub/k8s-image-awaiter
+```
+
+You don't have to explicitly specify the tag, as the existing tags
+will work. Note that this **only** works for *released* versions of
+z2jh - if you are using a *dev* version of z2jh, this will not work.
+
 ## 3.1
 
 ### 3.1.0 - 2023-09-29