Update README.md (#292)

* Update README.md

@kadikraman We're adding maintenance status to all of our repos. "Active" is appropriate for this one. Let me know if you have any questions

* Update README.md

Author: boygirl

README.md

@@ -5,6 +5,8 @@
 <br><br>
 
 [![npm package version](https://badge.fury.io/js/react-native-app-auth.svg)](https://badge.fury.io/js/react-native-app-auth)
+[![Maintenance Status][maintenance-image]](#maintenance-status)
+
 
 #### This is the API documentation for `react-native-app-auth >= 4.0.`
 
@@ -404,3 +406,12 @@ Some authentication providers, including examples cited below, require you to pr
 
 Having said this, in some cases using client secrets is unavoidable. In these cases, a `clientSecret` parameter can be provided to `authorize`/`refresh` calls when performing a token request.
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+
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+#### Maintenance Status
+
+**Active:** Formidable is actively working on this project, and we expect to continue for work for the foreseeable future. Bug reports, feature requests and pull requests are welcome. 
+
+[maintenance-image]: https://img.shields.io/badge/maintenance-active-green.svg
+