Content inclusion shortcode example

content-shortcode.php

<?php

/**
 * Plugin Name: Content Shortcode
 **/

add_shortcode('content', function ($atts) {
    extract(shortcode_atts([
        'slug' => null,
        'post_type' => 'post',
    ], $atts));

    $post = get_page_by_path($slug, OBJECT, $post_type);

    if (!$post) {
        return sprintf(__('No content found for slug `%s` in `%s` post type.', 'your__text_domain'), $slug, $post_type);
    }

    return apply_filters('the_content', $post->post_content);
});