Multiple bug fixes

【Contents of the fix】
■Fixed a bug where optimization settings were not reflected correctly.
■【iPhone】Fixed a bug where the Hatena bookmark icon was not displayed on the share button in the fixed footer bar.
■Fixed a minor bug.

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

【Modified file】
css/footer-bar.css
functions/acceleration.php
style.css
template-parts/footer-bar.php

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