Add the copy button to pycon3 highlighted code blocks. (#64)

Author: JulienPalard

python_docs_theme/static/copybutton.js

@@ -5,6 +5,7 @@ $(document).ready(function() {
     var div = $('.highlight-python .highlight,' +
                 '.highlight-python3 .highlight,' +
                 '.highlight-pycon .highlight,' +
+                '.highlight-pycon3 .highlight,' +
                 '.highlight-default .highlight');
     var pre = div.find('pre');
 
@@ -61,4 +62,3 @@ $(document).ready(function() {
         }
     });
 });
-