Custom Marker with Mapdeck

Question

I am trying to create custom Markers (e.g. a picture or symbol) for a scatter plot in mapdeck.

Example:

  test <- st_as_sf(as.data.frame(list("lon" = 40, "lat" = 60)), coords = c("lon", "lat"))
  map <- mapdeck( style = mapdeck_style("light")) %>%
    add_geojson(test)

This plots a point with the standard purple circle:

Now I want instead of the circle an awesome marker or something similar. I already tried to expand the sf by

test$["marker-symbol"] <- "rocket"

Which does not work. Is there anyway to customize the markers in mapdeck?