Added a short guide to migrating to OpenSearch Data Prepper from Open…

… Distro Data Prepper.

Signed-off-by: David Venable <[email protected]>

docs/getting_started.md

@@ -1,5 +1,9 @@
 # Getting Started with Data Prepper
 
+If you are migrating from Open Distro Data Prepper,
+visit the [Migrating from Open Distro](migrating_from_opendistro.md) page.
+Otherwise, please continue.
+
 ## Installation
 
 There are two ways to install Data Prepper for running.

docs/migrating_from_opendistro.md

@@ -0,0 +1,25 @@
+# Migrating from Open Distro Data Prepper
+
+Starting with Data Prepper 1.1, there is only one distribution of
+Data Prepper - Open Search Data Prepper. This document is here to help existing users migrate
+from the old Open Distro Data Prepper to OpenSearch Data Prepper.
+
+
+### Change your Pipeline Configuration
+
+The `elasticsearch` sink has changed to `opensearch`. You will
+need to change your existing pipeline to use the `opensearch` plugin
+instead of `elasticsearch`.
+
+Please note that while the plugin is titled `opensearch` it remains compatible
+with Open Distro and ElasticSearch 7.x.
+
+### Update Docker Image
+
+The Open Distro Data Prepper Docker image was located at `amazon/opendistro-for-elasticsearch-data-prepper`.
+You will need to change this value to `opensearchproject/opensearch-data-prepper`.
+
+## More Information
+
+You can find more information about Data Prepper configurations
+by going to the [Getting Started](getting_started.md) guide.