Suggestion: icon markers

Leaflet provides icon markers. This would be nice to have in plotly.

Code taken from https://rstudio.github.io/leaflet/markers.html. That webpage contains the rendered output.

library(leaflet)
# Make a list of icons. We'll index into it based on name.
oceanIcons <- iconList(
  ship = makeIcon("ferry-18.png", "ferry-18@2x.png", 18, 18),
  pirate = makeIcon("danger-24.png", "danger-24@2x.png", 24, 24)
)

# Some fake data
df <- sp::SpatialPointsDataFrame(
  cbind(
    (runif(20) - .5) * 10 - 90.620130,  # lng
    (runif(20) - .5) * 3.8 + 25.638077  # lat
  ),
  data.frame(type = factor(
    ifelse(runif(20) > 0.75, "pirate", "ship"),
    c("ship", "pirate")
  ))
)

leaflet(df) %>% addTiles() %>%
  # Select from oceanIcons based on df$type
  addMarkers(icon = ~oceanIcons[type])

Beginne damit, das angeforderte Verhalten mit dem verlinkten Leaflet icon-markers-Beispiel und den vorhandenen plotly.R marker APIs zu vergleichen. Bestimme den unterstützten Umfang der Icon-Auswahl und wie die Fertigstellung demonstriert würde; das Issue nennt keine Dateien oder Tests.