markdown: Change the copy icon to a check once copied (#25970)

This PR makes it so the copy icon on code blocks will change to a check
once the code block has been copied.

Release Notes:

- N/A
fc5ff318e3Marshall Bowers committed on 3/4/2025, 12:14:26 AM· committed by GitHubparente7b3b8b
1 file changedLine totals unavailable