Added RawContainer support to changelog (#375)

CHANGELOG/CHANGELOG-v0.5.0.md

@@ -9,6 +9,7 @@
 - [Single Task Execution](https://flyte.readthedocs.io/en/latest/user/features/single_task_execution.html) to enable registering and launching tasks outside the scope of a workflow to enable faster iteration and a more intuitive development workflow.
 - [Run to completion](https://flyte.readthedocs.io/en/latest/user/features/on_failure_policy.html) to enable workflows to continue executing even if one or more branches fail.
 - Fixed retries for dynamically yielded nodes.
+- PreAlpha Support for Raw container with FlyteCoPilot. (docs coming soon). [Sample Notebooks](https://github.com/lyft/flytekit/blob/master/sample-notebooks/raw-container-shell.ipynb). This makes it possible to run workflows with arbitrary containers
 
 ## Plugins
 - Cleaned up Presto executor to send namespace as user to improve queueing