Classiaditor nie jest zdefiniowany za pomocą NPM

Regarding Laravel included libraries examples in boostrap.js file such as 
pusher, axios, etc...

You may use :
window.ClassicEditor = require('@ckeditor/ckeditor5-build-classic');

$(document).ready(function(){
  ClassicEditor.create($('#edit_about_text').get()[0]);
});
Lokesh003