Add document describing how to deprecate packages

[RickWinter]

Add instructions on how to deprecate modules into a document at /doc/deprecation.md (or similar).
Link the page in our repo to the Azure SDK "Deprecating Azure SDKs" page.

General SDK patterns for deprecation should be followed.

Do not duplicate information that is already in the https://azure.github.io/azure-sdk/policies_support.html document. Link to the relevant sections.

[github-actions]

Hi @RickWinter, we deeply appreciate your input into this project. Regrettably, this issue has remained unresolved for over 2 years and inactive for 30 days, leading us to the decision to close it. We've implemented this policy to maintain the relevance of our issue queue and facilitate easier navigation for new contributors. If you still believe this topic requires attention, please feel free to create a new issue, referencing this one. Thank you for your understanding and ongoing support.