tsu_newsletter_block/src/index.js

import { registerBlockType } from '@wordpress/blocks';
import metadata from './block.json';

import { useBlockProps, RichText } from '@wordpress/block-editor';
import ServerSideRender from '@wordpress/server-side-render';

registerBlockType(metadata.name, {
    edit: () => {
        return (
            <div { ...useBlockProps() }>
                <ServerSideRender
                    block="tsu-plugins/newsletter"
                    // attributes={ attributes }
                    urlQueryArgs={ {
                        // Let the render callback knows that this is an editor preview.
                        preview: 1,
                        // In the preview mode, get_the_ID() does not work (it returns a
                        // `false`), hence let's send the post ID.
                        // post_id: context.postId,
                    } }
                />
            </div>
        );
    },
    save: () => {
        return ("Tutaj renderujemy blok newsletter.");
    }
});