charm store ui should render actions.yaml content

[ryan-beisner]

For quite a long time, the charm store web ui has presented the config.yaml description content.

However, the description content from actions.yaml is not exposed and the effect on UX is that many users aren't even aware of the available actions on a charm, and what those actions do.

Please add actions.yaml web ui rendering in the same way as config.yaml rendering.

Thank you.

[frankban]

I think this is a good idea, and we'll need some design directions.