title: Column widths in renderDataTable of a shiny app without stretching
body: <p>I would like to get a DataTable (with all its ranking, search and page features) that does not stretch fully across the page, and results in large amounts of white space in each column...</p>
  
  <p><img src="https://i.stack.imgur.com/rl2cL.png" alt="enter image description here"></p>
  
  <p>... ideally with column widths similar to the "wrap" style from <code>renderTable</code>...</p>
  
  <p><img src="https://i.stack.imgur.com/bfLwO.png" alt="enter image description here"></p>
  
  <p>I know I can fix relative column widths, however, my table will dynamically update with different numbers of columns dependent of inputs selected. I would prefer additional columns to expand into the empty space on the right hand side and then trigger a horizontal scrollbar if it becomes wider than the browser window width.</p>
  
  <p>Reproducible example of the tables in the images above...</p>
  
  <pre><code>library(shiny)
  runApp(list(
    ui = navbarPage(
    title = 'Tables',
    tabPanel('dataTableOutput', dataTableOutput('ex1')),
    tabPanel('tableOutput', tableOutput('ex2'))
  ),
  server = function(input, output) {
    output$ex1 &lt;- renderDataTable(iris)
    output$ex2 &lt;- renderTable(iris)
  }
  ))
  </code></pre>