Show language name instead of value as tooltip when hovering over markers on the map

[alerikaisattera]

When hovering over markers on the map, tooltips display feature values. This is rather inconvenient, it would be much better to display language names

[xrotwang]

The tooltip shows language names on the "languages" map at https://grambank.clld.org/languages
While I agree that on the Grambank maps - with typically just two different values - the feature values aren't very informative, the language name is just one click away on these maps, too.