Display the date a map was created

[Aurelie-Jallut]

Is your feature request related to a problem? Please describe.
On some of the maps I consult, I find that there's a lack of context as to the freshness of the data displayed, if no information has been entered in the legend.

Describe the solution you'd like
Make it possible to display the date the map was created and perhaps also the date it was last updated.
This information could appear in the legend

[yohanboniface]

The tricky part is that the last modification date of the map is not the freshness of the data, but of the metadata, given the data itself can come from elsewhere… :/