Save selected countries

[MaximMoinat]

Either in the cache or as in the url, to make a direct link to a certain selection of countries to load on the dashboard. For instance to bookmark this and quickly get an update on your selected countries. Even nicer would be to also save the state of the other visualisation parameters (e.g. the cases/recovered/deaths toggles, weeks, etc.).

Also, could be nice to open a random set of (three) countries when opening the main page.

[rnugraha]

Thx, like the idea!