Add support for Ckeditor 5

@saidatom, ya your merge request looks good

with that said, I no longer see the widget icon for embed_block in the ckeditor5 , the above patch fixes an error message but doesn't solve ckeditor5 compatibility completely

see message after switching from ckeditor4 to ckeditor5

Warning message

The CKEditor 4 button EmbedBlock does not have a known upgrade path. If it allowed editing markup, then you can do so now through the Source Editing functionality.

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mshaik → changed the visibility of the branch 3316336-add-support-for to hidden.

mshaik → changed the visibility of the branch 3316336-add-support-for to hidden.