Allowed for user defined axis positions. Closes plotly#2029

Author: moutikabdessabour

R/ggplotly.R

@@ -753,6 +753,7 @@ gg2list <- function(p, width = NULL, height = NULL,
         gridwidth = unitConvert(panelGrid, "pixels", type),
         zeroline = FALSE,
         anchor = anchor,
+        side = scales$get_scales(xy)$position,
         # layout.axisid.title don't yet support alignment :(
         title = list(
           text = faced(axisTitleText, axisTitle$face),