docs: Embedding in existing react App (#1626)

Added how to embed OHIF viewer in an existing React application

docs/latest/deployment/recipes/embedded-viewer.md

@@ -126,12 +126,39 @@ globally defined styles/scripts.
 > We're trying to embed the OHIF Viewer into an existing React App, but seeing
 > react-dom and react conflicts. What can we do?
 
+If you are installing OHIF viewer inside another react app, you may use `installViewer` as follows:
+```
+import { installViewer } from '@ohif/viewer'
+
+const ohifViewerConfig = window.config // or set it here
+const containerId = 'ohif'
+const componentRenderedOrUpdatedCallback = function() {
+    console.log('OHIF Viewer rendered/updated');
+};
+
+componentDidMount() {
+   installViewer(
+      ohifViewerConfig,
+      containerId,
+      componentRenderedOrUpdatedCallback
+    );
+}
+
+render () {
+   ...
+   //you can render in any element you wish
+   <AnyTag id={containerId}/>
+}
+
+```
+
 `installViewer` is a convenience method that pulls in some dependencies that may
 not be compatible with existing `react` apps. `@ohif/viewer` also exports `App`
 which is a react component that takes the `configuration` outlined above as
 props. You can use it as a reusable component, and to avoid `react` version
 conflict issues.
 
+
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