Add map functionality

[Playmojs]

Some method for adding a map should exist in edit mode. This should for instance be available when creating a marker or a parent map, but possibly also just as a button in edit mode. Maps should have

• A main image (the map). This should be easy to add, for instance with drag-and-drop.
• A related article. This article can be new (its own issue), should it also support linking an existing article to a map?
• A map title
• Any other map features I haven't thought of?

Potentially, the new map should also encourage an initial marker or a parent map, so the user can't be stuck in a map. If the map is created as a parent map or from a marker in another map, it should be easy to create a link back to this other map from the new map.

[Playmojs]

We should also determine if maps can exist without the info listed above. In that case, creating a new map would simply refer the user to a black background (a blank map, with only an id), where adding the necessary information can be done in edit mode. Changing map image, title or article should be possible from edit mode anyway.