Enabled custom HTML head content to work within editors

Closes #562

resources/assets/js/pages/page-form.js

@@ -97,6 +97,17 @@ function registerEditorShortcuts(editor) {
 
 }
 
+/**
+ * Load custom HTML head content from the settings into the editor.
+ * @param editor
+ */
+function loadCustomHeadContent(editor) {
+    window.$http.get(window.baseUrl('/custom-head-content')).then(resp => {
+        if (!resp.data) return;
+        let head = editor.getDoc().querySelector('head');
+        head.innerHTML += resp.data;
+    });
+}
 
 /**
  * Create and enable our custom code plugin
@@ -322,6 +333,9 @@ module.exports = {
             args.content = '';
         }
     },
+    init_instance_callback: function(editor) {
+        loadCustomHeadContent(editor);
+    },
     setup: function (editor) {
 
         editor.on('init ExecCommand change input NodeChange ObjectResized', editorChange);