title: Bootstrap 4 : Add a subtitle to a modal
body: <p>I'm actually building a web site and I use Bootstrap since it's very efficient and ensure a possibility for everyone to know how my website works.</p>
  
  <p>But the fact is that I'm trying to use a modal to display some stuffs and I need to put in this one a subtitle, I've already tried few stuffs but any of them was working properly.</p>
  
  <p>My ideal modal would look like this :</p>
  
  <p><img src="https://i.imgur.com/eZzObU1.png" alt="My ideal modal"></p>
  
  <p>I guess the solution is in the HTML &amp; CSS files but I'm a newbie to those work ways so even with reading the Bootstrap official CSS modal's page I didn't managed to find the way to do it.</p>
  
  <h2>I've already tried :</h2>
  
  <ul>
  <li>Adding another title <code>div</code> inside of the modal header and editing a bit the css but didn't managed to get what I'm looking for 
  
  <ul>
  <li>tried using the <code>width</code> property to force the title to take the whole row but didn't worked.</li>
  <li>tried using the <code>justify-content</code> attribute since we're using flexboxes but didn't worked too.</li>
  </ul></li>
  <li>Adding directly an other title (<code>h5</code>) inside of the header, but had the same result than for the <code>div</code></li>
  </ul>
  
  <p>Thanks in advance for your time and help.</p>