Multiple bug fixes

【Contents of the fix】
■Fixed a bug where the font color of the category label was not reflected when the header content was set as a split slider.
■Fixed an error display on My Page when using WelcartPay, Lumise, and Zeus payment modules.
■Added a pager to the contributors list page.

The following are the files that have been modified for this update.
【Corrected files】
functions/welcart.php
style.css
template-parts/page-template-type5.php
wc_templates/member/wc_member_page.php