Replace Rover position marker with custom icon

[logbasem]

Currently, on the RoverMap, the marker for the Rover's current position as added here...

 currentPositionMarker = L.marker([lat, lon]).addTo(map);

...uses the default styling/marker icon for its display. This is a problem, because the waypoint functionality also uses the default marker, making it extremely difficult to differentiate between a waypoint and the Rover's position. So, we need to use a custom icon for the Rover's position. Ideally, something red and kind of small, but idk honestly up to you! It just needs to be different from the other and easily identifiable.