Add sample code disclaimer to readme (#386)

Author: geoffg-sentry

README.md

@@ -43,3 +43,6 @@ Sentry.init({ dsn: '___PUBLIC_DSN___' });
 * [Installation](https://docs.sentry.io/platforms/javascript/guides/cordova/#install)
 * [Using Sentry with Ionic](https://docs.sentry.io/platforms/javascript/guides/cordova/ionic/)
 * [Documentation](https://docs.sentry.io/platforms/javascript/guides/cordova/)
+
+> [!WARNING]
+> Example and sample code in is unmaintained. Sample code may contain security vulnerabilities, should never be used in production, and exists only for illustrative purposes.