Multiple bug fixes

【Contents of the fix】
■Adjustments to the contributor profile at the bottom of the article
 ・Fine tuning of styles
 ・Fixed a bug that target=”_blank” was not applied to external links.
 ・Changed the output content of the contributor profile from catchphrase to profile information.
■Fixed a bug where the layout of the category mega menu would collapse when the thumbnail hover effect was set to no fade/animation.
■Changed specifications so that the number of “big posts” displayed in the blog list on the top page can be changed.
■Tweaked the font size of each heading tag.
■Replaced the web font (icon) for Facebook.

The following files have been modified for this update.
【Modified files】
admin/inc/front_page.php
css/sns-botton.css
functions/head.php
template-parts/navigation.php
front-page.php
functions.php
single.php
style.css