Improved WYSIWYG code block behaviour via range of fixes

- Fixed issues with new code blocks breaking or acting odd due to
  misnamed contenteditable attribute.
- Helped fix issue where code blocks may show in a strage blank state
  due to timing within shadow dom loading.
- Fixed some function timing issues where some functions required their
  async predecessor to have finished.

Tested rather heavily in firefox and brave.
Fixes #3292

resources/js/components/code-editor.js

@@ -59,12 +59,10 @@ class CodeEditor {
         this.languageInput.value = language;
         this.callback = callback;
 
-        this.show();
-        this.updateEditorMode(language);
-
-        window.importVersioned('code').then(Code => {
-            Code.setContent(this.editor, code);
-        });
+        this.show()
+            .then(() => this.updateEditorMode(language))
+            .then(() => window.importVersioned('code'))
+            .then(Code => Code.setContent(this.editor, code));
     }
 
     async show() {