Support isso comment system

[mdosch]

Thank you for this lightweight and simple blogging platform.
I would appreciate if you could add support for isso: https://github.com/isso-comments/isso

[danpros]

Hello,

If you already have isso server running than we just need to modify 2 files: main.html.php (the index file) if you need to display the comments count and post.html.php (individual blog post).

Reading from their docs. Add below script in main.html.php and post.html.php:

<script data-isso="//comments.example.tld/"
        src="//comments.example.tld/js/embed.min.js"></script>

For comment counter:

<a href="<?php echo $p->url;?>#isso-thread">Comments</a>

For comment form:

<section id="isso-thread">
    <noscript>Javascript needs to be activated to view comments.</noscript>
</section>