title: Way to use calendar format for numeric data input in Shiny?
body: <p>Is there a way to use the calendar input layout (ala <code>dateInput()</code>) for non-date data?</p>
  
  <p>Specifically, I want to be able to open the calendar view but instead of dates, there be a grid of possible input values to select from. </p>
  
  <p>The resulting graphic, if possible, would open like this:</p>
  
  <p><a href="https://i.stack.imgur.com/41lBw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/41lBw.png" alt="calendar inputDate selector"></a></p>
  
  <p>(Note: the #'s are arbitrary and random in the above picture)</p>
  
  <p>I've looked at the code for <code>dateInput</code>, but it wasn't immediately apparent how I would start converting the code in a way to use input values instead of dates...</p>