Suggestion: Open in Codepen buttons should be links (<a>)

If possible, the "Open in Codepen" buttons are implemented as `` elements, but should be `` elements. This would:

- Provide a more-accurate representation of what they do (navigate you do a different page), improving accessibility
- Be a better semantic representation of their purpose, for the same reason
- Allow users the control to use them in the way that suits them best, e.g. right-click and "Bookmark link...", "Save link as..." etc., or drag-and-drop the link into a specific other tab or window

Find the 'Open in Codepen' buttons in the codebase, likely in HTML or Nunjucks template files. Change the button elements to anchor tags while preserving their styling and functionality. Verify the change by checking that the buttons still work and open Codepen correctly, and that they can be right-clicked or dragged as links.

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