Add installation instructions

README.md

@@ -5,3 +5,9 @@
 This package provides an automatically configured [client for OpenSearch](https://opensearch.org/docs/latest/clients/javascript/index/) in an [Architect](https://arc.codes/) application.
 
 Pair this package with [@nasa-gcn/architect-plugin-search](https://github.com/nasa-gcn/architect-plugin-search), a [plugin](https://arc.codes/docs/en/guides/plugins/overview) that adds [Amazon OpenSearch](https://aws.amazon.com/opensearch-service/) to your application.
+
+## To install
+
+```
+npm i @nasa-gcn/architect-functions-search
+```