update to higlight.js 8.4

vendor/assets/javascripts/highlight_js/languages/erb.js

@@ -0,0 +1,26 @@
+/*
+Language: ERB (Embedded Ruby)
+Requires: xml.js, ruby.js
+Author: Lucas Mazza <lucastmazza@gmail.com>
+Contributors: Kassio Borges <kassioborgesm@gmail.com>
+Description: "Bridge" language defining fragments of Ruby in HTML within <% .. %>
+Category: template
+*/
+
+function(hljs) {
+  return {
+    subLanguage: 'xml', subLanguageMode: 'continuous',
+    contains: [
+      {
+        className: 'comment',
+        begin: '<%#', end: '%>',
+      },
+      {
+        begin: '<%[%=-]?', end: '[%-]?%>',
+        subLanguage: 'ruby',
+        excludeBegin: true,
+        excludeEnd: true
+      }
+    ]
+  };
+}