docs: Add OpenCensus to OpenTelemetry shim to README (#879)

* Add OpenCensus to OpenTelemetry shim to README * line width

Author: zoercai

README.md

@@ -214,7 +214,12 @@ dependency to collect the data and exporter dependency to export to backend.
 
 [Click here](https://medium.com/google-cloud/troubleshooting-cloud-spanner-applications-with-opencensus-2cf424c4c590) for more information.
 
+### OpenTelemetry
 
+To use OpenTelemetry with the Cloud Spanner client, set up the OpenTelemetry pipeline, and add 
+the [OpenCensus shim](https://github.com/open-telemetry/opentelemetry-java/tree/main/opencensus-shim)
+to your project. Follow the [README instructions](https://github.com/open-telemetry/opentelemetry-java/blob/main/opencensus-shim/README.md)
+to set up traces and metrics.
 
 
 ## Samples