Controls the thickness of the route line, its outline, the section lines and the instruction
lines at all zoom levels. Each preset is a zoom profile of its own, tuned so the outline stays a
readable rim at every thickness. A widthFactor multiplies whichever preset applies.
Available options:
"s" - Thin line, suitable for dense or cluttered maps"m" - Default medium thickness"l" - Thick line, useful for high emphasis or accessibility
Route line thickness preset.