changelog update for community contribution (Azure#26507)

Author: christothes

sdk/identity/Azure.Identity/CHANGELOG.md

@@ -3,14 +3,20 @@
 ## 1.6.0-beta.1 (Unreleased)
 
 ### Features Added
-- `EnvironmentCredential` now supports certificate subject name / issuer based authentication with `AZURE_CLIENT_SEND_CERTIFICATE_CHAIN` environment variable.
+- `EnvironmentCredential` now supports certificate subject name / issuer based authentication with `AZURE_CLIENT_SEND_CERTIFICATE_CHAIN` environment variable (A community contribution, courtesy of _[trevorlacey-msft](https://github.com/trevorlacey-msft))_. 
 
 ### Breaking Changes
 
 ### Bugs Fixed
 
 ### Other Changes
 
+### Acknowledgments
+
+Thank you to our developer community members who helped to make Azure Identity better with their contributions to this release:
+
+- Trevor Lacey _([GitHub](https://github.com/trevorlacey-msft))_
+
 ## 1.5.0 (2021-10-14)
 
 ### Breaking Changes from 1.5.0-beta.4