Update codeit.js

Author: benhatsor

lib/codeit.js

@@ -221,8 +221,10 @@ class CodeitElement extends HTMLElement {
         if (textToHighlight !== '') {
 
           let highlightLang = Prism.util.getLanguage(elToHighlight);
-
-
+          
+          if (highlightLang === 'none') highlightLang = 'plain';
+          
+          
           let highlightHTML = Prism.highlight(textToHighlight,
                                               Prism.languages[highlightLang],
                                               highlightLang);