Multiple bug fixes / extended plugin support

【Contents of fixes】
■Support for extended plug-ins
 ・WCEX Auto Delivery
 ・WCEX Multiple Shipping
 ・WCEX Coupon
 ・WCEX Widget Cart
■Fixed a bug that occurred when using the extension plugins “WCEX SKU Select” and “WCEX Multi Price” together.
■Fixed a bug in which banner content could not be added in the content builder of the theme option “Top Page”.
■Fixed the bug that the recommended products were not displayed on the detail page even if “Show recommended products on product detail page” was checked in the recommended products setting of the theme option “Welcart Products”.
■Fixed a bug that the cart button was sometimes displayed on the left side of the product detail page when the body of the page was long.
■Fixed an issue where the layout would collapse when tabbed product details on the product detail page were set to tab 5.
■Changed specifications so that the background color can be changed for each page displayed in the recommended products setting.
■Fixed minor bugs.

The following are the files that have been modified for this update.
【Corrected files】
admin/inc/contents-builder.php
admin/inc/footer.php
admin/inc/welcart.php
admin/js/contents-builder.js
admin/js/footer-bar.js
admin/theme-options.php
footer.php
functions/welcart.php
js/functions.js
languages/ja.mo
languages/ja.po
style.css
template-parts/page-template-type3.php
template-parts/recommend-items.php
wc_templates/cart/wc_customer_page.php
wc_templates/member/wc_member_page.php
wc_templates/member/wc_new_member_page.php
wc_templates/wc_item_single.php
wc_templates/wc_sku_select.php

【Added files】
auto_delivery.css
wc_templates/member/wc_autodelivery_history_page.php
wc_templates/member/wc_member_msa_page.php
wcex_multi_shipping.css