Added support for table of contents in blog posts (#1278)

![image](https://user-images.githubusercontent.com/31376482/226411600-e5619108-3842-4c44-b582-61fcc94a1b0c.png)

---------

Signed-off-by: George Araújo <george.gcac@gmail.com>

Gemfile

@@ -12,6 +12,7 @@ group :jekyll_plugins do
     gem 'jekyll-paginate-v2'
     gem 'jekyll-scholar'
     gem 'jekyll-sitemap'
+    gem 'jekyll-toc'
     gem 'jekyll-twitter-plugin'
     gem 'jemoji'
     gem 'mini_racer'

_config.yml

@@ -220,11 +220,12 @@ plugins:
   - jekyll-email-protect
   - jekyll-feed
   - jekyll-imagemagick
+  - jekyll-link-attributes
   - jekyll-minifier
   - jekyll-paginate-v2
   - jekyll/scholar
   - jekyll-sitemap
-  - jekyll-link-attributes
+  - jekyll-toc
   - jekyll-twitter-plugin
   - jemoji
 

_layouts/post.html

@@ -40,7 +40,15 @@ layout: default
   </header>
 
   <article class="post-content">
-    {{ content }}
+    {% if page.toc %}
+    <div id="table-of-contents">
+      {% toc %}
+    </div>
+    <hr>
+    {% endif %}
+    <div id="markdown-content">
+      {{ content }}
+    </div>
   </article>
 
   {%- if site.related_blog_posts.enabled -%}

_posts/2023-03-20-table-of-contents.md

@@ -0,0 +1,35 @@
+---
+layout: post
+title: a post with table of contents
+date: 2023-03-20 11:59:00-0400
+description: an example of a blog post with table of contents
+categories: sample-posts toc
+giscus_comments: true
+related_posts: false
+toc: true
+---
+This post shows how to add a table of contents.
+
+## Adding a Table of Contents
+
+To add a table of contents to a post, simply add `toc: true` to the front matter of the post. The table of contents will be automatically generated from the headings in the post.
+
+### Example of Sub-Heading 1
+
+Jean shorts raw denim Vice normcore, art party High Life PBR skateboard stumptown vinyl kitsch. Four loko meh 8-bit, tousled banh mi tilde forage Schlitz dreamcatcher twee 3 wolf moon. Chambray asymmetrical paleo salvia, sartorial umami four loko master cleanse drinking vinegar brunch. <a href="https://www.pinterest.com">Pinterest</a> DIY authentic Schlitz, hoodie Intelligentsia butcher trust fund brunch shabby chic Kickstarter forage flexitarian. Direct trade <a href="https://en.wikipedia.org/wiki/Cold-pressed_juice">cold-pressed</a> meggings stumptown plaid, pop-up taxidermy. Hoodie XOXO fingerstache scenester Echo Park. Plaid ugh Wes Anderson, freegan pug selvage fanny pack leggings pickled food truck DIY irony Banksy.
+
+### Example of another Sub-Heading 1
+
+Jean shorts raw denim Vice normcore, art party High Life PBR skateboard stumptown vinyl kitsch. Four loko meh 8-bit, tousled banh mi tilde forage Schlitz dreamcatcher twee 3 wolf moon. Chambray asymmetrical paleo salvia, sartorial umami four loko master cleanse drinking vinegar brunch. <a href="https://www.pinterest.com">Pinterest</a> DIY authentic Schlitz, hoodie Intelligentsia butcher trust fund brunch shabby chic Kickstarter forage flexitarian. Direct trade <a href="https://en.wikipedia.org/wiki/Cold-pressed_juice">cold-pressed</a> meggings stumptown plaid, pop-up taxidermy. Hoodie XOXO fingerstache scenester Echo Park. Plaid ugh Wes Anderson, freegan pug selvage fanny pack leggings pickled food truck DIY irony Banksy.
+
+## Table of Contents Options
+
+If you want to learn more about how to customize the table of contents, you can check the [jekyll-toc](https://github.com/toshimaru/jekyll-toc) repository.
+
+### Example of Sub-Heading 2
+
+Jean shorts raw denim Vice normcore, art party High Life PBR skateboard stumptown vinyl kitsch. Four loko meh 8-bit, tousled banh mi tilde forage Schlitz dreamcatcher twee 3 wolf moon. Chambray asymmetrical paleo salvia, sartorial umami four loko master cleanse drinking vinegar brunch. <a href="https://www.pinterest.com">Pinterest</a> DIY authentic Schlitz, hoodie Intelligentsia butcher trust fund brunch shabby chic Kickstarter forage flexitarian. Direct trade <a href="https://en.wikipedia.org/wiki/Cold-pressed_juice">cold-pressed</a> meggings stumptown plaid, pop-up taxidermy. Hoodie XOXO fingerstache scenester Echo Park. Plaid ugh Wes Anderson, freegan pug selvage fanny pack leggings pickled food truck DIY irony Banksy.
+
+### Example of another Sub-Heading 2
+
+Jean shorts raw denim Vice normcore, art party High Life PBR skateboard stumptown vinyl kitsch. Four loko meh 8-bit, tousled banh mi tilde forage Schlitz dreamcatcher twee 3 wolf moon. Chambray asymmetrical paleo salvia, sartorial umami four loko master cleanse drinking vinegar brunch. <a href="https://www.pinterest.com">Pinterest</a> DIY authentic Schlitz, hoodie Intelligentsia butcher trust fund brunch shabby chic Kickstarter forage flexitarian. Direct trade <a href="https://en.wikipedia.org/wiki/Cold-pressed_juice">cold-pressed</a> meggings stumptown plaid, pop-up taxidermy. Hoodie XOXO fingerstache scenester Echo Park. Plaid ugh Wes Anderson, freegan pug selvage fanny pack leggings pickled food truck DIY irony Banksy.