update CHANGELOG

CHANGELOG.md

@@ -9,6 +9,12 @@ IMPROVEMENTS:
    image pulls [[GH-4192](https://github.com/hashicorp/nomad/issues/4192)] 
  * env: Default interpolation of optional meta fields of parameterized jobs to
    an empty string rather than the field key. [[GH-3720](https://github.com/hashicorp/nomad/issues/3720)]
+ * core: Add a new [progress_deadline](https://www.nomadproject.io/docs/job-specification/update.html#progress_deadline) parameter to
+   support rescheduling failed allocations during a deployment. This allows operators to specify a configurable deadline before which
+   a deployment should see healthy allocations [[GH-4259](https://github.com/hashicorp/nomad/issues/4259)]
+ * core: Canary allocations are tagged in Consul to enable
+   using service tags to isolate canary instances during deployments [[GH-4259](https://github.com/hashicorp/nomad/issues/4259)]
+
 
 BUG FIXES:
  * api/client: Fix potentially out of order logs and streamed file contents