title: How to format a number 0..9 to display with 2 digits (it's NOT a date)
body: <p>I'd like to always show a number under 100 with 2 digits (example: 03, 05, 15...)</p>
  
  <p>How can I append the 0 without using a conditional to check if it's under 10?</p>
  
  <p>I need to append the result to another String, so I cannot use printf.</p>