共有ボタンはBloggerの機能にもあるのですが、デザインや対応しているものが古い感じがするので、直接タグを編集して実装したメモ。
<style>
.sns-share-buttons {
text-align: center;
font-size: 14px;
font-family: Helvetica,"游ゴシック",YuGothic,"Hiragino Kaku Gothic ProN",Meiryo,sans-serif;
}
.sns-share-buttons-inner:after {
content: ".";
display: block;
clear: both;
height: 0;
visibility: hidden;
}
.sns-share-buttons-inner{
display:flex;
justify-content:space-around;
}
.sns-share-buttons-inner a{
box-sizing: border-box;
display: block;
width: 18%;
padding: .7em 0;
color: white;
text-decoration: none;
text-align: center;
border-radius:6px;
font-weight: bold;
}
.sns-share-buttons-inner a,
.sns-share-buttons-inner a:link,
.sns-share-buttons-inner a:visited,
.sns-share-buttons-inner a:hover,
.sns-share-buttons-inner a:active,
.sns-share-buttons-inner a:focus{
color: white !important;
}
.sns-btn.sns-btn-twitter{
background: #1B95E0;
}
.sns-btn.sns-btn-line{
background: #1dcd00;
}
.sns-btn.sns-btn-facebook{
background: #3b5998;
}
.sns-btn.sns-btn-pocket{
background: #ee4056;
}
.sns-btn.sns-btn-hatena{
background: #008FDE;
}
.sns-btn {
-webkit-transition: 0.3s ease-in-out;
-moz-transition: 0.3s ease-in-out;
-o-transition: 0.3s ease-in-out;
transition: 0.3s ease-in-out;
}
.sns-btn:hover {
opacity: 0.6;
filter: alpha(opacity=60);
}
/* 画面サイズが768px以上の時 */
@media only screen and (min-width: 768px) {
.sns-btn::after {
font-weight: bold;
margin-left: 0.25em;
}
.sns-btn.sns-btn-facebook::after{
content: 'Facebook';
}
.sns-btn.sns-btn-line::after{
content: 'LINE';
}
.sns-btn.sns-btn-twitter::after{
content: 'Twitter';
}
.sns-btn.sns-btn-pocket::after{
content: 'Pocket';
}
.sns-btn.sns-btn-hatena::after{
content: 'Hatena';
}
}
</style>
アイコンにFont Awesomeを使うのでkitを作成してこちらも貼り付け。

Font Awesome
The internet's icon library + toolkit. Used by millions of designers, devs, & content creators. Open-source. Always free. Always awesome.
<script crossorigin='anonymous' src='https://kit.fontawesome.com/0123456789.js'/>
(※以下のコードはサンプルです。)
<div class='sns-share-buttons'>
<h4 style='text-align:center;'>Shareボタン</h4>
<div class='sns-share-buttons-inner'>
<!-- Twitter -->
<a class='sns-btn sns-btn-twitter' expr:href='"http://twitter.com/share?url=" + data:post.url' expr:title='data:top.shareToTwitterMsg' rel='nofollow' target='_blank'><i aria-hidden='true' class='fab fa-twitter'/></a>
<!-- LINE -->
<a class='sns-btn sns-btn-line' expr:href='"http://line.me/R/msg/text/?" + data:post.url' rel='nofollow' target='_blank' title='LINE で共有する'><i aria-hidden='true' class='fab fa-line'/></a>
<!-- Facebook -->
<a class='sns-btn sns-btn-facebook' expr:href='"https://www.facebook.com/sharer/sharer.php?u=" + data:post.url' expr:onclick='"window.open(this.href, \"_blank\", \"height=430,width=640\"); return false;"' expr:title='data:top.shareToFacebookMsg' rel='nofollow' target='_blank'><i aria-hidden='true' class='fab fa-facebook'/></a>
<!-- Pocket -->
<a class='sns-btn sns-btn-pocket' expr:href='"https://getpocket.com/edit?url=" + data:post.url + "&title=" + data:post.title' rel='nofollow' target='blank' title='Pocket で共有する'><i aria-hidden='true' class='fab fa-get-pocket'/></a>
<!-- B! Hatena -->
<a class='sns-btn sns-btn-hatena' expr:href='"https://b.hatena.ne.jp/add?mode=confirm&url=" + data:post.url + "&title=" + data:post.title' rel='nofollow' target='_blank' title='Hatena で共有する'><i aria-hidden='true' class='fab fa-hatena' style='font-weight: bold;'>B!</i></a>
</div>
</div>


