Your buttons in ckeditor?

Question

JavaScript

Made according to the example from the documentation (create a plugin) - does not work.
I did it following the example from this video - it does not work
https://www.youtube.com/watch?v=RVmqR5G1wWc
I tried everything, probably, the button does not appear.
After I found this when entering the editor. There are no such errors in the admin panel itself. Thought it might be them.

What do you advise? Or can someone throw off the code of this page. I’ll replace it myself, I don’t know which way to dig at all.
One hundred percent error. was there before my manipulation. Moreover, I did not touch this file.
I can’t throw off the code, it’s too big, codepen swears.
That's if that's the whole file.
https://yadi.sk/d/Usgte_Ch3ZGw2y