doc: add installation instructions for npm (#532)

Prashoon123 · web-flow · commit 4ee23991bc14 · 2021-01-23T09:10:04.000+01:00
diff --git a/website/docs/Installation.md b/website/docs/Installation.md
@@ -9,6 +9,10 @@ sidebar_label: Installation
 ### Get library
 
 ```bash
+# with npm
+npm install @react-native-async-storage/async-storage
+
+# with yarn
 yarn add @react-native-async-storage/async-storage
 ```
 
