✨ Add lazy loading for highlightjs on code-block component

Mainly because highlight.js is a heavy library but only used
on a very concrete situations, so it does not make sense to load
it all the time.

frontend/src/app/util/code_highlight.cljs

@@ -0,0 +1,15 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC
+
+(ns app.util.code-highlight
+  (:require
+   ["highlight.js" :as hljs]
+   [app.util.dom :as dom]))
+
+(defn highlight!
+  [node]
+  (dom/set-data! node "highlighted" nil)
+  (hljs/highlightElement node))