update changelog

Author: virtualstaticvoid

CHANGELOG.md

@@ -1,6 +1,13 @@
 v?.?.? - ?? ??? ????
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+* Add `before_started`, `after_completed` and `after_failed` functionality.
+* Add `logger` helper method, available within task methods.
+* Use `SecureRandom.hex(10)` instead of `uuid` for shorter process and tasks IDs.
+* Bug fix for options on `sequential`, `concurrent`, `for_each` and `sub_process` methods.
+* Bug fix instrumentation payload.
+* Documentation updates.
+
 v0.5.1 - 06 Jan 2023
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 * Include process definition in processes, tasks and payloads to aid debugging.