Add a copy mind map button

[JannikStreek]

Proposed feature
Currently, maps can be shared to enable multi user sessions. However, currently it is not possible to copy a mind map with a similar mechanism. The idea would be: A button in the share modal with which you can create a new map with the same content as present in the current map. This enables a fast copy instead of exporting the Map, creating a new map and importing content.

•  Think about where to put the button in the share modal
• A click creates a new mind map with the same content (in a new tab?)

Additional context
Ecalidraw has a similar feature as a reference. Click on "save as" and then on as a link.