add changelog entry

CHANGELOG.md

@@ -2,12 +2,17 @@
 
 ## dev
 
-Version <dev> brings support for gleaning a Docker container id from cgroups v2 based containers.
+Version <dev> brings support for gleaning a Docker container id from cgroups v2 based containers and records additional synthetics attributes.
 
 - **Feature: Enhance Docker container id reporting**
 
   Previously, the agent was only capable of determining a host Docker container's ID if the container was based on cgroups v1. Now, containers based on cgroups v2 will also have their container IDs reported to New Relic. [PR#2229](https://github.com/newrelic/newrelic-ruby-agent/issues/2229).
 
+- **Feature: Updates events with additional synthetics attributes when available**
+
+  The agent will now record additional synthetics attributes on synthetics events if these attributes are available.  [PR#2203](https://github.com/newrelic/newrelic-ruby-agent/pull/2203)
+
+
 ## v9.5.0
 
 Version 9.5.0 introduces Stripe instrumentation, allows the agent to record additional response information on a transaction when middleware instrumentation is disabled, introduces new `:'sidekiq.args.include'` and `:'sidekiq.args.exclude:` configuration options to permit capturing only certain Sidekiq job arguments, updates Elasticsearch datastore instance metrics, and fixes a bug in `NewRelic::Rack::AgentHooks.needed?`.