Add contributing section w/ maintainers & approvers (aws-observability#922)

Fixes aws-observability#920

Author: Alex Boten

README.md

@@ -97,3 +97,26 @@ The following are runtimes which are no longer or not yet supported by this repo
 [2]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/faas.md#incoming-invocations
 [3]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/faas.md#outgoing-invocations
 [4]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/faas-metrics.md#faas-invocations
+
+## Contributing
+
+See the [Contributing Guide](CONTRIBUTING.md) for details.
+
+Here is a list of community roles with current and previous members:
+
+- Approvers ([@open-telemetry/lambda-extension-approvers](https://github.com/orgs/open-telemetry/teams/lambda-extension-approvers)):
+
+   - [Tristan Sloughter](https://github.com/tsloughter), Splunk
+   - [Tyler Benson](https://github.com/tylerbenson), Lightstep
+
+- Emeritus Approvers:
+
+   - [Lei Wang](https://github.com/wangzlei), AWS
+   - [Nathaniel Ruiz Nowell](https://github.com/NathanielRN), AWS
+
+- Maintainers ([@open-telemetry/lambda-extension-maintainers](https://github.com/orgs/open-telemetry/teams/lambda-extension-maintainers)):
+
+   - [Alex Boten](https://github.com/codeboten), Lightstep
+   - [Anthony Mirabella](https://github.com/Aneurysm9), AWS
+
+Learn more about roles in the [community repository](https://github.com/open-telemetry/community/blob/main/community-membership.md).