Implement HTML ruby tags for east-asian languages (#30897)

lib/sanitize_ext/sanitize_config.rb

@@ -65,7 +65,7 @@ class Sanitize
     end
 
     MASTODON_STRICT = freeze_config(
-      elements: %w(p br span a del pre blockquote code b strong u i em ul ol li),
+      elements: %w(p br span a del pre blockquote code b strong u i em ul ol li ruby rt rp),
 
       attributes: {
         'a' => %w(href rel class translate),