Multiple bug fixes

【Contents of the fix】
■【iPhone】 Fixed a bug that sometimes the page transition does not work unless the button is tapped twice.
■【iPhone】Fixed a bug where the Hatena bookmark icon was not displayed on the share button in the fixed footer bar.

The following are the files that have been fixed for this update.

【Modified file】
css/footer-bar.css
footer.php
functions/update_notifier.php
languages/ja.mo
languages/ja.po
style.css
template-parts/footer-bar.php

【Added files】
img/common/hatenabookmark-logomark.svg