title: line break and subscript in axis title using plotly in R
body: <p>I just started to use <code>plotly</code> for some interactive scatter plots in R and having a hard time on axis labels. Normally I designed my plots with <code>ggplot2</code> and then using the <code>ggplotly</code> function to convert them, but this is sometimes very slow for any reason. So I want to create my plots directly in <code>plotly</code>...</p>
  
  <p>I am trying now to change the axis title and want to add line breaks and later I also want to add subscript labels. But I am already failing at the newline in the title. Is there any trick?</p>
  
  <pre><code>library(plotly)
  library(dplyr)
  plot_ly(mtcars, x = wt, y = mpg, text = rownames(mtcars), mode = "text") %&gt;%
    layout(xaxis=list(title='text with\nlinebreak'))
  </code></pre>