TYPO3 Core

CKEditor should be loaded via a plain <script async> tag in
preparation for a transition away from requirejs to ES6 modules.

CKEditor v4 is not available as ES6 module and can not easily
be transformed into a strict-mode compatible module.
CKEditor v4 requires `this` to be the global window object
in various functions, but `this` is not bound to the global
window object in strict-mode (as implied by <script type="module">).

Note: CKEditor is not a real AMD module anyway, but is configured
to be shimed by requirejs to be loadable as AMD module,
therefore it can safely be loaded using good old <script>.