Example container block

demo.php

<?php
/**
 * Plugin Name:     Internationalization Block
 * Description:     This is some demo for i18n support.
 * Version:         0.1.0
 * Author:          ryelle
 * License:         GPL-2.0-or-later
 * License URI:     https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain:     ryelle-i18n
 *
 * @package         ryelle-i18n
 */

namespace Ryelle\I18N_Block;

/**
* Break the world.
*/
function register_block() {
	$dir = dirname( __FILE__ );

	wp_register_script(
		'ryelle-i18n-i18n-demo-block-editor',
		plugins_url( 'index.js', __FILE__ ),
		array('wp-block-editor', 'wp-blocks', 'wp-element', 'wp-i18n', 'wp-polyfill'),
		time()
	);
	wp_set_script_translations( 'ryelle-i18n-i18n-demo-block-editor', 'ryelle-i18n' );

	wp_register_style(
		'ryelle-i18n-i18n-demo-block',
		plugins_url( 'style.css', __FILE__ ),
		array(),
		filemtime( __DIR__ . '/style.css' )
	);

	register_block_type( 'ryelle-i18n/i18n-demo', array(
		'editor_script' => 'ryelle-i18n-i18n-demo-block-editor',
		'style'         => 'ryelle-i18n-i18n-demo-block',
	) );
}
add_action( 'init', __NAMESPACE__ . '\register_block' );

/**
 * Restrict allowed blocks on all post types, for testing.
 */
add_filter(
	'allowed_block_types',
	function( $allowed_block_types ) {
		return array(
			'core/paragraph',
			// This plugin block.
			'ryelle-i18n/i18n-demo',
			// Some blocks from wordpress.org.
			'book-review-block/book-review',
			'a8c/starscape'
		);
	}
);

index.js

/**
 * WordPress dependencies
 */
const { __ } = wp.i18n;
const { InnerBlocks } = wp.blockEditor;
const { registerBlockType } = wp.blocks;
const { createElement } = wp.element;

/**
 * Every block starts by registering a new block type definition.
 *
 * @see https://developer.wordpress.org/block-editor/developers/block-api/#registering-a-block
 */
registerBlockType("ryelle-i18n/i18n-demo", {
	title: __("Internationalization Block", "ryelle-i18n"),
	description: __("This is some demo for i18n support.", "ryelle-i18n"),
	category: "common",
	icon: "admin-site-alt2",
	supports: {
		html: false,
	},

	edit: ({ className }) => {
		/* Core blocks, plus one block-directory block */
		const ALLOWED_BLOCKS = ["core/image", "core/heading", "core/paragraph", "book-review-block/book-review"];
		/* Create a template from core blocks. */
		const TEMPLATE = [
			[
				"core/heading",
				{ level: 2, placeholder: __("Your Title", "ryelle-i18n") },
			],
		];

		return createElement(
			"div",
			{ className: className },
			createElement(InnerBlocks, {
				allowedBlocks: ALLOWED_BLOCKS,
				template: TEMPLATE,
				template_lock: false,
			})
		);
	},

	save: () => {
		return createElement(
			"div",
			{},
			createElement(InnerBlocks.Content)
		);
	},
});

style.css

.wp-block-ryelle-i18n-i18n-demo {
	background-color:var(--wp-admin-theme-color);
	color:#fff;
	padding:2px
}