Multiple bug fixes

【Contents of fixes】
■Added support for WP5.6 (compatible with jQuery version upgrade)
■Changed Facebook OGP setting from old specification (fb:admins) to new specification (fb:app_id).
※Please refer to the following article about how to get “fb:app_id” (application ID).
 How to get the fb:app ID required for Facebook OGP settings
■OGP tag optimization
■【Mac】Fixed a bug that Japanese and European characters may be displayed with different thickness when using some fonts.

The following are the files that have been modified for this update.
【Modified file】
admin/theme-options.php
comments.php
editor-style-03.css
functions/head.php
functions/ogp.php
functions/seo.php
languages/ja.mo
languages/ja.po
pagebuilder/assets/css/pagebuilder.css
style.css
widget/ad.php
widget/archive_dropdown.php
widget/category_list.php
widget/custom_menu.php
widget/google_search.php
widget/styled_post_list1.php
widget/styled_post_list2.php
widget/styled_post_list3.php
widget/tab_post_list.php
widget/user_profile.php

【Added files】
js/jquery.easing.1.4.js