✨ 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>

theme.toml

@@ -224,6 +224,11 @@ encode_plaintext_email = true  # Setting is ignored if email is already encoded.
 #     { name = "spotify", url = "https://open.spotify.com/artist/5Hv2bYBhMp1lUHFri06xkE", icon = "spotify" },
 # ]
 
+# Fediverse profile.
+# Adds metadata to feature the author's profile in Mastodon link previews.
+# Example: for @username@example.com, use:
+# fediverse_creator = { handle = "username", domain = "example.com" }
+
 # Extra menu to show on the footer, below socials section.
 # footer_menu = [
 #     {url = "about", name = "about", trailing_slash = true},