application.js: make the clipboard button selector more restrictive.

assets/js/src/application.js

@@ -54,7 +54,7 @@
     })
 
     // Insert copy to clipboard button before .highlight
-    $('.highlight').each(function () {
+    $('figure.highlight, div.highlight').each(function () {
       var btnHtml = '<div class="bd-clipboard"><button class="btn-clipboard" title="Copy to clipboard">Copy</button></div>'
       $(this).before(btnHtml)
       $('.btn-clipboard')