Following T257503, the TemplateData dialog has a panel for editing maps, as a JSON in a text area.
As a next step, we should have separate text areas for editing each map, and make it easier to add a map, delete a map and edit a map's contents.
- The maps panel has a menu containing the names of the maps, and a text area for editing the JSON of a single map
- Clicking on a map name fills the text area with that map's details
- It is possible to add a new map
- It is possible to delete a map
- If there are no maps, there is an option to add a map and a message explaining that there are no maps