Added OTel resourc env var documentation

Author: jeremydvoss

azure-monitor-opentelemetry/README.md

@@ -144,6 +144,8 @@ Samples are available [here][samples] to demonstrate how to utilize the above co
 [ot_instrumentation_urllib3]: https://github.com/open-telemetry/opentelemetry-python-contrib/tree/main/instrumentation/opentelemetry-instrumentation-urllib3
 [ot_instrumentation_urllib3_version]: https://github.com/open-telemetry/opentelemetry-python-contrib/blob/main/instrumentation/opentelemetry-instrumentation-urllib3/src/opentelemetry/instrumentation/urllib3/package.py#L16
 [opentelemetry_spec_resource]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#resource-sdk
+[opentelemetry_spec_resource_attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable
+[opentelemetry_spec_service_name]: https://github.com/open-telemetry/opentelemetry-specification/tree/main/specification/resource/semantic_conventions#semantic-attributes-with-sdk-provided-default-value
 [opentelemetry_spec_view]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#view
 [pip]: https://pypi.org/project/pip/
 [pypi_django]: https://pypi.org/project/Django/