proposal for supporting resource references (#1057)

Issue #545 

Description of changes:

* Proposal for handling resource relationship in ACK custom resources.
* View the rendered proposal [here](https://github.com/vijtrip2/community/blob/res-rel-proposal/docs/design/proposals/resource-reference/resource-reference.md)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Author: vijtrip2