[ECS] [request]: A comment/description field for task definitions and their versions

### Community Note

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**Tell us about your request**
We would like to have a comments/description field for task definitions and their versions.

**Which service(s) is this request for?**
ECS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
In Task Defs with loads of config, when creating new ones over time, it's not easy to see what's changed between task defs, so you end up with a massive list. Sometimes there are configuration that is then later useful to switch between task defs.
If there were a comment field when creating a new one, this could be used to indicate the changes between task defs.
This would make them easier to manage too in terms of clarity on what can be deleted; when viewing the list if there were a comment column.
We would like to have a comment/description field for each task definition, which would be shown on the task definition list in the AWS Console and a comment/description field for each version of a task definition, which would be shown on the task definition version list.

**Are you currently working around this issue?**
Spending time to find a task definition version with the necessary parameters.