✨ feat: add fediverse creator metadata support (#409)

Add `fediverse_creator` variable to highlight author's fediverse profile in Mastodon link previews.

Co-authored-by: Ariel Richtman <Ariel.Richtman@SilverRailTech.com>
Co-authored-by: welpo <welpo@users.noreply.github.com>

templates/partials/header.html

@@ -174,6 +174,11 @@
         {%- include "partials/analytics.html" -%}
     {%- endif -%}
 
+    {# Socials #}
+    {%- if config.extra.fediverse_creator -%}
+        <meta name="fediverse:creator" content="@{{ config.extra.fediverse_creator["handle"] }}@{{ config.extra.fediverse_creator["domain"]}}" />
+    {%- endif -%}
+
     {# Search #}
     {%- if config.build_search_index -%}
         {%- if config.search.index_format -%}