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 in which the pager of the archive page was not displayed correctly when using a smartphone.
■Adjusting the layout of the Theme Options screen

【Modified files】
admin/css/my_admin.css
mobile/navigation.php
mobile/style-mobile.css
functions.php
style.css