added warning about named groups, which are only introduced in ES9/2018

Author: Erwin Dondorp

saltgui/static/scripts/output/OutputDocumentation.js

@@ -261,10 +261,12 @@ export class OutputDocumentation {
 
         // replace ``......``
         // e.g. in "sys.doc state.apply"
+        // named groups are only introduced in ES9/2018
         out = out.replace(/``([^`]*)``/g, "<span style='background-color: #575757'>$1</span>");
 
         // replace `......`
         // e.g. in "sys.doc state.apply"
+        // named groups are only introduced in ES9/2018
         out = out.replace(/`([^`]*)`/g, "<span style='color: yellow'>$1</span>");
 
         // remove whitespace at end of lines