Updated codeblock editor to work with fade animation

- Added fadeIn to animation JS service.
- Updated overlay to use anim service and to recieve a callback for
after-anim actions.
- Updated code editor popup to refresh Codemirror instance layout after
animation has completed.

Fixes #1672

resources/js/services/code.js

@@ -258,10 +258,18 @@ function setMode(cmInstance, modeSuggestion, content) {
 function setContent(cmInstance, codeContent) {
     cmInstance.setValue(codeContent);
     setTimeout(() => {
-        cmInstance.refresh();
+        updateLayout(cmInstance);
     }, 10);
 }
 
+/**
+ * Update the layout (codemirror refresh) of a cm instance.
+ * @param cmInstance
+ */
+function updateLayout(cmInstance) {
+    cmInstance.refresh();
+}
+
 /**
  * Get a CodeMirror instance to use for the markdown editor.
  * @param {HTMLElement} elem
@@ -301,6 +309,7 @@ export default {
     popupEditor: popupEditor,
     setMode: setMode,
     setContent: setContent,
+    updateLayout: updateLayout,
     markdownEditor: markdownEditor,
     getMetaKey: getMetaKey,
 };