Multiple bug and specification fixes

【Contents of the fix】
■Add processing timing to update inventory status.
■Fixed a bug in WP5.8 that the setting field is not displayed after changing the fixed page template when using the block editor.
■Fixed a bug in which the style indicating that a button is currently selected is not applied on smartphones when the display format of SKUs created using the “WCEX SKU Select” plug-in is set to radio buttons.

【Modified files】
functions/page-lp-cf.php
functions/page-ranking-cf.php
functions/welcart.php
footer.php
style.css