Replace browser info window by modal

[geofranzi]

[EleonoraPetzold]

not clear what was meant here @geofranzi ?

[geofranzi]

There is/was a browser alert window instead of a modal. This is not urgent, but as this looks in every browser different should change (e.g. with refactoring to Svelte) by replacing it with a normal Modal window we use now for confirmation / or toasts for information.