title: Plotly scaleY not working across subplot rows
body: <p>Building up on another question (<a href="https://stackoverflow.com/questions/57253488/how-to-remove-duplicate-legend-entries-w-plotly-subplots">How to remove duplicate legend entries w/ plotly subplots()</a>), I am facing a new problem. I want all plots in both rows to have the same Y-axis. However, If I turn "shareY = TRUE", the plots on the upper row share an axis, and the plots on the lower row do, but the axis differ from one another.  </p>
  
  <p>The code is basically the one from the answer by @Joris Chau, but added "shareY = TRUE" on the last line.  </p>
  
  <pre><code>library(plotly)
  library(tidyverse)
  
  mpg %&gt;%
    mutate_at("trans", as.factor) %&gt;%  
    group_by(class) %&gt;%
    group_map(.f = ~{          
      ## fill missing levels w/ displ = 0, cyl = first available value 
      complete(.x, trans, fill = list(displ = 0, cyl = head(.x$cyl, 1))) %&gt;%
        plot_ly(x = ~cyl, y = ~displ, color = ~trans, colors = "Paired", type = "bar",
                showlegend = (.y == "2seater"), legendgroup = ~trans) %&gt;%
        layout(yaxis = list(title = as.character(.y)), barmode = "stack")
    }) %&gt;%
    subplot(nrows = 2, shareX = TRUE, shareY = TRUE, titleY = TRUE)   
  </code></pre>
  
  <p>How can I tell plotly to use the same scale across all plots?</p>