title: R Leaflet leave markers on top
body: <p>Hi I am trying to have multiple layers to a map in Leaflet R while leaving the markers as the top most layer. I tried using bringToFront() in highlightOptions() for the addCircleMarkers option but they get moved to the bottom most layer whenever I change the layer using addLayersControl().</p>
  
  <p>Suggestions?</p>
  
  <pre><code>renderLeaflet(
  
  leaflet()%&gt;%
    addTiles()%&gt;%
    addPolygons(data = district_shapes, 
                weight = 1,
                fillColor = "blue",
                fillOpacity = .25,
                label = labels,
                group = "School District"
                ) %&gt;%
    addPolygons(data = district_shapes, 
                weight = 1,
                fillColor =~frl_pal(district_shapes$FRL),
                fillOpacity = .7,
                label = labels,
                popup = frl_label,
                group = "Free and Reduced Lunch"
                ) %&gt;%
    addPolygons(data = district_shapes, 
                weight = 1,
                fillColor =~avgIncome_pal(district_shapes$Avg_Household_Income),
                fillOpacity = .7,
                label = labels,
                group = "Average Household Income"
                ) %&gt;%
    addLayersControl(
      baseGroup = c("School District","Free and Reduced Lunch", "Average Household Income"),
      options = layersControlOptions(collapsed = TRUE)
    )%&gt;%
    addCircleMarkers(
      lng = ~Longitude ,
      lat = ~Latitude,
      data = charter_year_filter(),
      label = ~Account_Name,
      color = ~Color,
      popup = sprintf("&lt;strong&gt;&lt;u&gt;%s&lt;/u&gt;&lt;/strong&gt;&lt;br/&gt;%s &lt;br/&gt;%s &lt;br/&gt;%s &lt;br/&gt;%s",
                    charter_geo$Account_Name, 
                    charter_geo$Site1, 
                    charter_geo$Site2,
                    charter_geo$Site3, 
                    charter_geo$Site4)%&gt;% lapply(htmltools::HTML),
      stroke = T,
      options = highlightOptions(bringToFront = T),
      opacity = 1,
      fillOpacity = .5,
      fill = T,
      clusterOptions = markerClusterOptions()
    )
  )
  </code></pre>