route geometry hides the map

Currently we offer the button on the right side to hide the route and see the underlying path.

One other interesting idea (from Susanne) would be to use two lines instead (maybe not as default but as another option of that button)

Try it [here](https://graphhopper.com/maps-dev/two_line_path/).

Open the linked two_line_path demo and trace the existing right-side button that hides the route to understand the current map behavior. Define and implement the additional two-line route display option, then verify that the underlying path remains visible when it is selected.

Written by the indexing model from the issue text.