Lines with gaps appear filled in legend

[1ec5]

A road under construction is depicted as a double line at high zoom levels, but in the legend, the double line appears filled in:

This is because the road construction line layer specifies the line-gap-width paint property:

https://github.com/ZeLonewolf/openstreetmap-americana/blob/820a1fe4c206c60cb32a12ea9ff83cef4be94e49/src/layer/construction.js#L48-L56

The legend currently uses this property to calculate the overall width of the line feature for sizing the generated SVG image, but it doesn’t actually separate the line into two lines:

https://github.com/ZeLonewolf/openstreetmap-americana/blob/b21979c3cb15066d362936c3abe53425e93b51d3/src/js/legend_control.js#L381-L389