Update changelog

CHANGELOG.md

@@ -3,6 +3,7 @@
 This file needs to be updated with every significant pull request. It is used to write down release notes.
 
 ## Version 0.5.7
+* Update data contract to align with latest schema
 
 ## Version 0.5.6
 * Expose request id to parent Rack application when using `ApplicationInsights::Rack::TrackRequest` middleware through `env['ApplicationInsights.request.id']`.