insert new segment using drag and drop from bottom panel

[kfarr]

idea: add layer panel can have a special category for street segments in which are the 7 or so cards for each of the default segment types (drive-lane, bus-lane, etc.)

could this be accomplished with the existing drag and drop panel?

the function would need to see the collided entity "drop zone" and get the segment and its position in the street by index id, then to add the actual street using the function from #976