Add plugin to CKeditor5 in Angular 8 Project

Hello there ,
i am web developer and i need to add a CodeBlock Plugin to the Ckeditor5 but i cannot do this ,
i already installed custom build but when i am changing anything in src/ckeditor.js nothing happen no effect
i was following these instructions
https://ckeditor.com/docs/ckeditor5/latest/builds/guides/development/custom-builds.html
and here is the source of the package build which i am using it's already custom build that what i see and have all files we need but when i import in into the component and add the plugin into the src/ckeditor.js nothing happen
https://github.com/ckeditor/ckeditor5-build-classic
i believe this gonna take one Hour or two
i hope we get this done
this need expert person or someone did this before
take a look at the images