[lint demo] Upgrade jshint

Issue #6857

Author: marijnh

demo/lint.html

@@ -9,7 +9,7 @@
 <script src="../lib/codemirror.js"></script>
 <script src="../mode/javascript/javascript.js"></script>
 <script src="../mode/css/css.js"></script>
-<script src="https://unpkg.com/jshint@2.9.6/dist/jshint.js"></script>
+<script src="https://unpkg.com/jshint@2.13.2/dist/jshint.js"></script>
 <script src="https://unpkg.com/[email protected]/web/jsonlint.js"></script>
 <script src="https://unpkg.com/[email protected]/dist/csslint.js"></script>
 <script src="../addon/lint/lint.js"></script>
@@ -150,7 +150,7 @@ <h2>Linter Demo</h2>
     lineNumbers: true,
     mode: "javascript",
     gutters: ["CodeMirror-lint-markers"],
-    lint: true
+    lint: {options: {esversion: 2021}},
   });
 
   var editor_json = CodeMirror.fromTextArea(document.getElementById("code-json"), {