feat(SEO): add SEO and SMO meta keywords in site's home page

Signed-off-by: Pablo Iranzo Gómez <Pablo.Iranzo@gmail.com>

Author: iranzo

THANKS.md

@@ -30,6 +30,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
 
 <!-- markdownlint-enable -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
 This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!

templates/base.html

@@ -24,6 +24,7 @@
         {% from '_includes/_defaults.html' import SITE_DESCRIPTION with context %}
         {% if SITE_DESCRIPTION %}
         <meta name="description" content="{% block head_description %}{{ SITE_DESCRIPTION|e }}{% endblock head_description %}" />
+        <meta name="twitter:description" content="{% block head_description2 %}{{ SITE_DESCRIPTION|e }}{% endblock head_description2 %}">
         {% endif %}
         {% block meta_tags_in_head %}
         {% from '_includes/_defaults.html' import TWITTER_USERNAME with context %}

templates/index.html

@@ -7,26 +7,22 @@
 {% block meta_tags_in_head %}
 {{ super() }}
 {% from '_includes/_defaults.html' import LANDING_PAGE_TITLE with context %}
-{% if LANDING_PAGE_TITLE  %}
+{% if LANDING_PAGE_TITLE %}
 <meta property="og:title" content="{{ LANDING_PAGE_TITLE|e }}"/>
 <meta name="twitter:title" content="{{ LANDING_PAGE_TITLE|e }}">
 {% else %}
 <meta property="og:title" content="{{ SITENAME|striptags|e }}"/>
 <meta name="twitter:title" content="{{ SITENAME|striptags|e }}">
 {% endif %}
 <meta property="og:url" content="{{ SITEURL }}" />
-{% from '_includes/_defaults.html' import SITE_DESCRIPTION with context %}
-{% if SITE_DESCRIPTION %}
-<meta property="og:description" content="{{SITE_DESCRIPTION|e}}" />
-<meta name="twitter:description" content="{{SITE_DESCRIPTION|e}}">
-{% endif %}
 <meta property="og:site_name" content="{{ SITENAME|striptags|e }}" />
 <meta property="og:article:author" content="{{ AUTHOR }}" />
 {% from '_includes/_defaults.html' import FEATURED_IMAGE with context %}
 {% if FEATURED_IMAGE %}
 <meta property="og:image" content="{{FEATURED_IMAGE}}" />
 <meta name="twitter:image" content="{{FEATURED_IMAGE}}" >
 {% endif %}
+<meta name="keywords" content="{% for tag, _ in tags|sort %} {{ tag }}, {% endfor %}{% for category, _ in categories|sort %} {{ category }}, {% endfor %}" />
 {% endblock meta_tags_in_head %}
 
 {% block content %}