Multiple bug fixes and feature additions

【Contents of the fix】
■【iPhone】Fixed a bug where the Hatena bookmark icon was not displayed on the share button in the fixed footer bar.
■Added language link function.
※The language link function has been added to the theme options. Some of the settings are different, but please refer to the following articles as well.
 Article in TOKI demo site: Language link setting function for speedy introduction of multilingualism .
■Fixed a bug that caused radio buttons to be unchecked during certain operations in some parts of the theme options.

The following files have been modified for this update.

【Modified file】
admin/assets/css/my_admin.css
admin/assets/css/my_admin.min.css
admin/assets/js/my_script.js
admin/assets/js/my_script.min.js
admin/inc/header.php
admin/theme-options.php
assets/css/footer-bar.css
assets/css/footer-bar.min.css
functions.php
header.php
inc/footer-bar.php
inc/update_notifier.php
inc/widgets/google_search.php
languages/ja.mo
languages/ja.po
style.css

【Added files】
admin/inc/lang.php
admin/assets/images/cn.png
admin/assets/images/de.png
admin/assets/images/es.png
admin/assets/images/fr.png
admin/assets/images/jp.png
admin/assets/images/kr.png
admin/assets/images/pt.png
admin/assets/images/ru.png
admin/assets/images/uk.png
admin/assets/images/us.png
assets/images/hatenabookmark-logomark.svg
assets/js/jscript.js