Added some even relevant seo tags to the page head (#84)

- Added twitter user name to get twitter tags included as well
Signed-off-by: Hofi <hofione@gmail.com>

Author: mrgarris0n

_config.yml

@@ -215,6 +215,9 @@ kramdown:
 atom_feed:
   hide: true
 
+twitter:
+  username: sngOSE
+
 # https://jch.penibelst.de/
 compress_html:
   profile: true

_includes/seo.html

@@ -47,7 +47,11 @@
   {%- assign og_type = "website" -%}
 {%- endif -%}
 
+<meta name="robots" content="index, follow">
+
 <title>{{ seo_title | default: site.title }}{% if paginator %}{% unless paginator.page == 1 %} {{ title_separator }} {{ site.data.ui-text[site.locale].page | default: "Page" }} {{ paginator.page }}{% endunless %}{% endif %}</title>
+<meta itemprop="name" content="{{ seo_title | default: site.title }}">
+<meta itemprop="description" content="{{ seo_description }}">
 <meta name="description" content="{{ seo_description }}">
 
 {% if author.name %}