Multiple bug fixes

【Contents of the fix】
■Fixed a bug where the text in the “Description (Message Area)” in the “Message” content of the Top Page content builder would be covered by the content below if it was too long.
■Fixed a bug in WP5.8 that the setting field is not displayed after changing the fixed page template when using the block editor.
■Supports the “Contact Form 7 Multi-Step Forms” plug-in.

【Modified files】
css/design-plus.css
style.css