refs https://github.com/TryGhost/Ghost/issues/9311
- add `{{koenig-card-markdown}}` component that renders an auto expanding textarea with the markdown card value
- add `{{card-markdown}}` that is an alias of `{{koenig-card-markdown}}` for backwards compatibility - all of our pre-1.0 alpha cards and our current markdown implementation do not have the `koenig-` prefix in their card names
