Added Documentation section

Signed-off-by: julie-gordon <92888546+julie-gordon@users.noreply.github.com>

Author: julie-gordon

README.md

@@ -5,6 +5,12 @@ This reference implementation simulates an external service that imports files f
 - Reviewing the format of requests to and responses from an external service that implements the file input cloud storage extension
 - Seeing how the extension functions when invoked from Navigator
 
+## Documentation
+For documentation about the file input cloud storage extension, see:
+- [File input cloud storage extension overview](https://developers.docusign.com/extension-apps/extension-apps-101/supported-extensions/file-input-cloud-storage/)
+- [File input cloud storage extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/file-input-cloud-storage/)
+- [File input cloud storage extension Navigator test](https://developers.docusign.com/extension-apps/build-an-extension-app/test/functional-tests/file-input-cloud-storage-navigator/)
+
 ## Authentication
 This reference implementation supports two [authentication](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/) flows:
 * [Authorization Code Grant](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/#authorization-code-grant) – required for public extension apps
@@ -135,3 +141,4 @@ This type of test shows how the extension functions when invoked from an [extens
 
 
 
+