Feature request: highlight route type when hovered over

As a user I would love to be able to hover over a route type, ie. "Paved Road", and all of the paved roads show up on the map highlighted in some way or another. 

Currently a user can click on the route and it'll iterate through the different paved roads, but i'd like to be able to see them highlighted all at once. 

BTW - is any of cycle.travel open source? I am a developer myself so could probably have a go at implementing this. 

Thanks!