Multiple bug fixes / support for WP5.8 widget block editor

【Contents of the fix】
■Support for the WordPress 5.8 widget block editor
■Fixed a bug that sometimes prevented the blog list page from being displayed when the load screen was displayed.
■Supports the “Contact Form 7 Multi-Step Forms” plug-in.
■Adjusting the layout of the official Twitter button

【Modified files】
assets/js/load.js
assets/js/load.min.js
inc/footer.php
functions.php
style.css