title: Highcharter buttonTheme only applying to first button
body: <p>I'm trying to set the font size for the buttons in a highchart graph (made in R highcharter). My graph has several buttons to press for specific time intervals and a range selector. I've customized font size for the range selector pretty easily using inputStyle and labelStyle. (You'll have to trust me on this, since the code below doesn't bother inputting any data and so leaves the range selectors blank.) But <a href="https://api.highcharts.com/highstock/rangeSelector.buttonTheme" rel="nofollow noreferrer">buttonTheme</a>--the thing that <a href="https://jsfiddle.net/gh/get/library/pure/highcharts/highcharts/tree/master/samples/stock/rangeselector/styling/" rel="nofollow noreferrer">should</a> affect the time interval buttons--only affects the first of my buttons. You can see this, running the code below; &quot;1Y&quot; is much smaller than &quot;5Y,&quot; &quot;10Y,&quot; and &quot;Max.&quot; Any idea why this is?</p>
  <pre><code>library(highcharter)
  
  graph = highchart() %&gt;% 
        hc_rangeSelector(enabled = TRUE, 
                         buttonTheme = list(style = list(fontSize='6pt')),
                         buttons = list(
                           list(type = 'year', count = 1, text = '1Y'),
                           list(type = 'year', count = 5, text = '5Y'),
                           list(type = 'year', count = 10, text = '10Y'),
                           list(type = 'all', text = 'Max')),
                         inputStyle = list(fontSize='6pt'),
                         labelStyle = list(fontSize='6pt')
        )
  </code></pre>