How to add custom block?

[Karina1703]

I forked strapi-plugin-ckeditor and put in the /plugins folder.
I would like to add my custom block (https://ckeditor.com/docs/ckeditor5/latest/framework/tutorials/widgets/implementing-a-block-widget.html#demo)

But when I've added it in the code (https://github.com/ckeditor/ckeditor5-tutorials-examples/blob/main/block-widget/final-project/main.js), I'm getting a lot of errors

If there is a way to add custom block?

hook.js:608 CKEditorError: plugincollection-plugin-not-found {"plugin":{}}
Read more: https://ckeditor.com/docs/ckeditor5/latest/support/error-codes.html#error-plugincollection-plugin-not-found
    at ckeditor5.js:5:71027
    at ckeditor5.js:5:71083
    at Array.forEach (<anonymous>)
    at h (ckeditor5.js:5:70891)
    at Qa.init (ckeditor5.js:5:69374)
    at RC.initPlugins (ckeditor5.js:5:398620)
    at ckeditor5.js:5:783035
    at new Promise (<anonymous>)
    at RC.create (ckeditor5.js:5:782992)
    at CKEditor._createEditor (index.js:605:30) {phase: 'initialization', willEditorRestart: false}
overrideMethod @ hook.js:608
(anonymous) @ index.js:587
Promise.catch
_initializeEditor @ index.js:585
mount @ index.js:513
(anonymous) @ index.js:166
Promise.then
_lock @ index.js:162
_LifeCycleElementSemaphore2 @ index.js:104
_initLifeCycleSemaphore @ index.js:512
componentDidMount @ index.js:481
commitLayoutEffectOnFiber @ react-dom.development.js:23344
commitLayoutMountEffects_complete @ react-dom.development.js:24727
commitLayoutEffects_begin @ react-dom.development.js:24713
commitLayoutEffects_begin @ react-dom.development.js:24695
commitLayoutEffects_begin @ react-dom.development.js:24695
commitLayoutEffects @ react-dom.development.js:24651
commitRootImpl @ react-dom.development.js:26862
commitRoot @ react-dom.development.js:26721
finishConcurrentRender @ react-dom.development.js:26020
performConcurrentWorkOnRoot @ react-dom.development.js:25848
workLoop @ scheduler.development.js:266
flushWork @ scheduler.development.js:239
performWorkUntilDeadline @ scheduler.development.js:533
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hook.js:608 Semaphore mounting error: TypeError: Cannot read properties of null (reading 'plugins')
    at onReady (index.js:82:44)
    at Object.afterMount (index.js:517:11)
    at index.js:175:26