Modify the demo code when new layer is added to map

[AliyanH]

The demo code should be modified dynamically when a new layer is added to the map, this can include when users are pasting in new layers-/geojson/links to the map.

For example, when pasting the following geojson to the demo map (mapml-viewer demo), the code should dynamically be updated to reflect the change:
{"type": "Feature","properties": {"Name":"Natural Resources Canada"},"geometry": {"type":"Point","coordinates":[-75.705974,45.399963]}}

Open for discussion, all suggestions are welcomed.