chore(readme): add breaking changes warning
[![Slack](https://img.shields.io/badge/JOIN-SLACK-blue)](https://kubernetes.slack.com/messages/openebs)
[![built with nix](https://builtwithnix.org/badge.svg)](https://builtwithnix.org)
+## :warning: Breaking Changes
+
+On develop, there are breaking changes to the etcd key space which is used by the control-plane components and the
+io-engine to retain information about replicas which contain the correct volume data.
+An upgrade strategy is yet to be devised, but you may try these steps at your own risk:
+1. Stop the [mayastor-control-plane](https://github.com/openebs/mayastor-control-plane) components
+1. When the pool operator is no longer running, remove the finalyzers and delete all `MayastorPool` CR's
+1. Enable compatibility mode with the mayastor data replica information
+ ```bash
+ $> ETCDCTL_API=3 etcdctl put "/openebs.io/mayastor/apis/v0/clusters/$KUBE_SYSTEM_UID/namespaces/$NAMESPACE/CoreRegistryConfig/db98f8bb-4afc-45d0-85b9-24c99cc443f2"
+ '{"id":"db98f8bb-4afc-45d0-85b9-24c99cc443f2","registration":"Automatic", "mayastor_compat_v1": true}'
+ ```
+1. Move etcd data from `/namespace/$NAMESPACE/control-plane/` to `/openebs.io/mayastor/apis/v0/clusters/$KUBE_SYSTEM_UID/namespaces/$NAMESPACE/`
+1. Install the new version of mayastor-io-engine and [mayastor-control-plane](https://github.com/openebs/mayastor-control-plane) from [mayastor-extensions](https://github.com/openebs/mayastor-extensions)
+1. Recreate the `MayastorPools` with the new CRD type `DiskPool`
+
Table of contents:
==================
- [Quickly deploy it on K8s and get started](https://mayastor.gitbook.io)
