subplot should support non 2D-cartesian charts

[cpsievert]

subplot(plot_ly(z = ~volcano), plot_ly(z = ~volcano, type = "surface"))

[cpsievert]

More generally, subplot() should someday grow to support non 2D-cartesian charts, but this would likely need to be done on a case by case basis

trs <- names(Schema$traces)
axes <- lapply(trs, function(x) grep("^[a-z]axis$", names(Schema$traces[[x]]$attributes), value = TRUE))
trs[lengths(axes) == 0]

 [1] "pie"            "scatterternary" "scatter3d"      "surface"       
 [5] "mesh3d"         "cone"           "scattergeo"     "choropleth"    
 [9] "splom"          "parcoords"      "scattermapbox"  "sankey"        
[13] "table"          "scatterpolar"   "scatterpolargl" "area"