speice.io/_includes/footer.html

{% if page.layout == 'post' %}
{% comment %}Thanks to https://www.bytedude.com/jekyll-previous-and-next-posts/{% endcomment %}
<div class="container">
    <hr>
    <div class="post-nav">
        <div>
            {% if page.previous.url %}
            <a href="{{page.previous.url}}">&laquo;&nbsp;{{page.previous.title}}</a>
            {% endif %}
        </div>
        <div class="post-nav-next">
            {% if page.next.url %}
            <a href="{{page.next.url}}">{{page.next.title}}&nbsp;&raquo;</a>
            {% endif %}
        </div>
    </div>
</div>


<script type="text/javascript"
    src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
    </script>
{% endif %}