The entry is syntactically wrong. The description terms expect a list of values for each key.
Given that 'crossing' is not a main tag, the key shouldn't be featured in the list at all. I've added highway=crossing instead.
window_construction: "Window Construction"
winery: "Winery"
"yes": "Craft Shop"
- crossing: "Crossing"
emergency:
access_point: "Access Point"
ambulance_station: "Ambulance Station"
bus_stop: "Bus Stop"
construction: "Highway under Construction"
corridor: "Corridor"
+ crossing: "Crossing"
cycleway: "Cycle Path"
elevator: "Elevator"
emergency_access_point: "Emergency Access Point"