Feature request: support post.id for comments

[mincong-h]

Description

Currently, Jekyll TeXt Theme relies on variable post.key to enable the disqus comment and uses it as identifier for disqus. Although there is a warning in the documentation, it creates some confusion and additional effort for blog migration. This is because post.key is not a built-in variable of Jekyll. What about supporting page.id? page.id is a builtin variable and can be used for comments.

Suggestion

{%- if page.id and
  site.comments.disqus.shortname -%}

  <div id="disqus_thread"></div>
  <script>
  /**
  *  RECOMMENDED CONFIGURATION VARIABLES: EDIT AND UNCOMMENT THE SECTION BELOW TO INSERT DYNAMIC VALUES FROM YOUR PLATFORM OR CMS.
  *  LEARN WHY DEFINING THESE VARIABLES IS IMPORTANT: https://disqus.com/admin/universalcode/#configuration-variables*/
  var disqus_config = function () {
    this.page.url = '{%- include snippets/page-url.html -%}';
    this.page.identifier = '{{ page.id }}';
  };
  (function() { // DON'T EDIT BELOW THIS LINE
    var d = document, s = d.createElement('script');
    s.src = 'https://{{ site.comments.disqus.shortname }}.disqus.com/embed.js';
    s.setAttribute('data-timestamp', +new Date());
    (d.head || d.body).appendChild(s);
  })();
  </script>
  <noscript>Please enable JavaScript to view the <a href="https://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript>

{%- endif -%}