add yaml file and link

Author: Nadia-JSch

docs/integration/api-overview.mdx

@@ -8,3 +8,11 @@ Application Programming Interface (APIs) define a contract of service for a set
 :::info
 Please visit our **[API documentation](https://api.device42.com/)** for detailed information on using Device42 APIs.
 :::
+
+## Device42 Swagger Files
+
+The current version of the API is hosted at [api.device42.com](https://api.device42.com/).
+
+You can find the previous versions of our Swagger (OpenAPI) YAML files below:
+
+- [v19.05.10](/assets/files/d42-swagger-v190510.yaml)