Second take on Mobile First 3-Column Preview Card Component

This is my second take on this challenge with a few changes.

Here's what I've changed:

• Removed the article element from the page after I was told it was being used incorrectly.
• Changed my h1 headings to h2 as it can be reused.
• Added a visually hidden h1 title so I don't get accessibility warnings.
• Changed my <button class="btn"> to <a href="#" class="btn"> as these buttons are supposed to be directing viewers to different parts of the site.
• I changed the px value in my @media to em for improved accessibility.

A big Thank you to @vcarames for all the suggested changes on how to improve my coding.

As always all feedback is welcome and I'm grateful to everyone who takes the time to view and correct my code.