title: Writing R dataframes to excel files with multiple worksheets
body: <p>I am currently using <code>write_excel_csv2</code> from <code>readxl</code> to write a data.frame in R to an excel file.
  How can I write two data.frames to two worksheets within the same excel file?
  To give an example, how can I combine the following two files to one?</p>
  <pre><code>write_excel_csv2(mtcars[1:10,], file_name1)
  write_excel_csv2(mtcars[11:20,], file_name2)
  </code></pre>