Add themed logo (opensearch-project#54)

Signed-off-by: Miki <mehranb@amazon.com>

Author: Miki

README.md

@@ -5,7 +5,7 @@
 [![Forum](https://img.shields.io/badge/chat-on%20forums-blue)](https://discuss.opendistrocommunity.dev/c/Use-this-category-for-all-questions-around-machine-learning-plugins)
 ![PRs welcome!](https://img.shields.io/badge/PRs-welcome!-success)
 
-<img src="https://opensearch.org/assets/brand/SVG/Logo/opensearch_logo_default.svg" height="64px"/>
+<img src="https://opensearch.org/assets/img/opensearch-logo-themed.svg" height="64px">
 
 - [OpenSearch Anomaly Detection Dashboards Plugin](#opensearch-anomaly-detection-dashboards-plugin)
 - [Documentation](#documentation)