Outline library inclusion policy (#386)

CONTRIBUTING.md

@@ -1,5 +1,15 @@
 ## Contributing
 
+### Library Inclusion in the Erlang Contrib Repository Policy
+
+Maintaining libraries can be a demanding task. Due to the limited number of maintainers, any library added to the
+contrib repository must have an OpenTelemetry CNCF Erlang Contrib Approver or Maintainer as a sponsor. [Becoming a member](https://github.com/open-telemetry/community/blob/main/guides/contributor/membership.md) and approver is a simple
+process. Following approval, the library can be merged and you will be added as a codeowner for it.
+
+This policy has been enacted to be respectful of the maintainers' time and to ensure users get timely responses
+and regular updates. We want as many libraries to be under the official umbrella but need your commmitment to
+make that happen.
+
 ### Instrumenting a library
 
 When instrumenting a library, it is important to follow the [Trace Semantic Conventions](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/trace.md)