Tag and Category plugin for Jekyll

_cat_gen.rb

module Jekyll
  class CatIndex < Page
    def initialize(site, base, dir, cat)
      @site = site
      @base = base
      @dir = dir
      @name = 'index.html'
      self.process(@name)
      self.read_yaml(File.join(base, '_layouts'), 'cat_index.html')
      self.data['cat'] = cat
   end
  end
  class CatGenerator < Generator
    safe true
    def generate(site)
      if site.layouts.key? 'cat_index'
        dir = 'blog/categories'
        site.categories.keys.each do |cat|
          write_cat_index(site, File.join(dir, cat), cat)
        end
      end
    end
    def write_cat_index(site, dir, cat)
      index = CatIndex.new(site, site.source, dir, cat)
      index.render(site.layouts, site.site_payload)
      index.write(site.dest)
      site.pages << index
    end
  end
end

_tag_gen.rb

module Jekyll
  class TagIndex < Page
    def initialize(site, base, dir, tag)
      @site = site
      @base = base
      @dir = dir
      @name = 'index.html'
      self.process(@name)
      self.read_yaml(File.join(base, '_layouts'), 'tag_index.html')
      self.data['tag'] = tag
   end
  end
  class TagGenerator < Generator
    safe true
    def generate(site)
      if site.layouts.key? 'tag_index'
        dir = 'blog/tags'
        site.tags.keys.each do |tag|
          write_tag_index(site, File.join(dir, tag), tag)
        end
      end
    end
    def write_tag_index(site, dir, tag)
      index = TagIndex.new(site, site.source, dir, tag)
      index.render(site.layouts, site.site_payload)
      index.write(site.dest)
      site.pages << index
    end
  end
end

cat_index.html

---
layout: default
---

<style>
.tag .tag__title{
    margin-top:1rem;
}
.tag .tag__content a{
    display:inline-block;
    line-height:1.25em;
}
</style>

<div class="tag">
    <a class="tag__back" href="/">&lt;-- back</a>
    <h1 class="tag__title">All {{ page.cat }}</h1>
    <div class="tag__content">
      {% if site.categories[page.cat] %}
      <ul>
      {% for post in site.categories[page.cat] %}
        <li>
            <span class="date">{{ post.date | date: '%Y %b %d' }}</span> - <a href="{{ post.url }}">{{ post.title }}</a>
        </li>
      {% endfor %}
      </ul>
      {% else %}
        <p>There is no posts for this category.</p>
      {% endif %}
    </div>
</div>

snipplet_post.html

{% if page.tags %}
  <span> | </span>
  {% for tag in page.tags %}
    <span>
      <a href='/blog/tags/{{tag}}'>{{ tag }}</a>{% if forloop.last==false %}, {% endif %}
    </span>
  {% endfor %}
{% endif %}

tag_index.html

---
layout: default
---

<style>
.tag .tag__title{
    margin-top:1rem;
}
.tag .tag__content a{
    display:inline-block;
    line-height:1.25em;
}
</style>

<div class="tag">
    <a class="tag__back" href="/">&lt;-- back</a>
    <h1 class="tag__title">Posts tagged "{{ page.tag }}"</h1>
    <div class="tag__content">
      
      {% if site.tags[page.tag] %}
      <ul>
      {% for post in site.tags[page.tag] %}
        <li>
            <span class="date">{{ post.date | date: '%Y %b %d' }}</span> - <a href="{{ post.url }}">{{ post.title }}</a>
        </li>
      {% endfor %}
      </ul>
      {% else %}
        <p>There is no posts for this tag.</p>
      {% endif %}
    </div>
</div>

What's the related changes in the file "_config.yml"?
I only see the post https://ongspxm.gitlab.io/blog/2016/09/jekyll-tag-and-categories/ and code here. Tried, it does not work.