specific code with support for Gutenberg blocks

<?php
/*
Plugin Name: Site Plugin
Description: Site-specific code with support for Gutenberg blocks
Author: Shaun Palmer
Author URI: https://yourwebsite.com/
*/

class SP_SitePlugin {

    public function __construct() {
        // General hooks and actions
        add_filter('widget_text', [$this, 'execute_php'], 100);
        add_filter('widget_text', 'do_shortcode');
        add_action('pre_ping', [$this, 'disable_internal_ping']);
        add_filter('the_excerpt_rss', [$this, 'add_thumbnail_to_rss']);
        add_filter('the_content_feed', [$this, 'add_thumbnail_to_rss']);
        add_action('after_setup_theme', [$this, 'add_editor_styles']);
        add_filter('tiny_mce_before_init', [$this, 'override_mce_options']);
        add_action('admin_bar_menu', [$this, 'edit_toolbar'], 999);
        add_filter('upload_mimes', [$this, 'add_upload_mimes']);
        add_filter('manage_posts_columns', [$this, 'posts_columns'], 5);
        add_action('manage_posts_custom_column', [$this, 'posts_custom_columns'], 5, 2);
        add_action('admin_enqueue_scripts', [$this, 'admin_styles']);

        // Check if Gutenberg is available, and register blocks if so
        if (function_exists('register_block_type')) {
            add_action('init', [$this, 'register_gutenberg_blocks']);
        }
    }

    // Execute PHP in text widgets
    public function execute_php($html) {
        if (strpos($html, "<?php") !== false) {
            ob_start();
            eval("?>" . $html);
            $html = ob_get_contents();
            ob_end_clean();
        }
        return $html;
    }

    // Disable internal pingbacks
    public function disable_internal_ping(&$links) {
        $home = get_option('home');
        foreach ($links as $l => $link) {
            if (0 === strpos($link, $home)) {
                unset($links[$l]);
            }
        }
    }

    // Add featured image to RSS feed
    public function add_thumbnail_to_rss($excerpt) {
        global $post;
        $content = '<p>' . get_the_post_thumbnail($post->ID) . '</p>' . get_the_excerpt();
        return $content;
    }

    // Add editor styles
    public function add_editor_styles() {
        add_editor_style('custom-editor-style.css');
    }

    // Override TinyMCE options
    public function override_mce_options($initArray) {
        $opts = '*[*]';
        $initArray['valid_elements'] = $opts;
        $initArray['extended_valid_elements'] = $opts;
        return $initArray;
    }

    // Edit the admin toolbar
    public function edit_toolbar($wp_toolbar) {
        $wp_toolbar->remove_node('wp-logo');
        $wp_toolbar->remove_node('site-name');
        $wp_toolbar->remove_node('updates');
        $wp_toolbar->remove_node('comments');
        $wp_toolbar->remove_node('new-content');
        $wp_toolbar->remove_node('top-secondary');
    }

    // Add custom MIME types for file uploads
    public function add_upload_mimes($mimes) {
        $mimes['ott|odt|zip|ReaperThemeZip|ReaperConfigZip'] = 'application/octet-stream';
        return $mimes;
    }

    // Add a thumbnail column to the post table
    public function posts_columns($defaults) {
        $defaults['riv_post_thumbs'] = __('Thumbs');
        return $defaults;
    }

    public function posts_custom_columns($column_name, $id) {
        if ($column_name === 'riv_post_thumbs') {
            echo the_post_thumbnail('featured-thumbnail');
        }
    }

    // Add admin CSS
    public function admin_styles() {
        wp_register_style('sp_admin_stylesheet', plugins_url('/admin.css', __FILE__));
        wp_enqueue_style('sp_admin_stylesheet');
    }

    // Register Gutenberg blocks
    public function register_gutenberg_blocks() {
        // Block assets
        wp_register_script(
            'sp-gutenberg-block',
            plugins_url('/blocks/block.js', __FILE__),
            ['wp-blocks', 'wp-element', 'wp-editor'],
            filemtime(plugin_dir_path(__FILE__) . '/blocks/block.js')
        );

        wp_register_style(
            'sp-block-editor-styles',
            plugins_url('/blocks/editor.css', __FILE__),
            ['wp-edit-blocks'],
            filemtime(plugin_dir_path(__FILE__) . '/blocks/editor.css')
        );

        wp_register_style(
            'sp-block-styles',
            plugins_url('/blocks/style.css', __FILE__),
            [],
            filemtime(plugin_dir_path(__FILE__) . '/blocks/style.css')
        );

        // Registering block
        register_block_type('sp/custom-block', [
            'editor_script' => 'sp-gutenberg-block',
            'editor_style' => 'sp-block-editor-styles',
            'style' => 'sp-block-styles',
        ]);
    }
}

// Initialize the plugin
$SP_SitePlugin = new SP_SitePlugin();