adds trademark to readme (#2486)

Trademark added to readme file

Signed-off-by: Kyle J. Davis <[email protected]>

Author: stockholmux

README.md

@@ -6,6 +6,7 @@
   - [Code of Conduct](#code-of-conduct)
   - [License](#license)
   - [Copyright](#copyright)
+  - [Trademark](#trademark)
 
 ## Welcome!
 
@@ -36,3 +37,9 @@ This project is licensed under the [Apache v2.0 License](LICENSE.txt).
 ## Copyright
 
 Copyright OpenSearch Contributors. See [NOTICE](NOTICE.txt) for details.
+
+## Trademark
+
+OpenSearch is a registered trademark of Amazon Web Services.
+
+OpenSearch includes certain Apache-licensed Elasticsearch code from Elasticsearch B.V. and other source code. Elasticsearch B.V. is not the source of that other source code. ELASTICSEARCH is a registered trademark of Elasticsearch B.V.