Add af, gd and si locales (#16090)

* Add af, gd and si locales

* i18n-tasks normalize

* Fix inconsistent interpolations

Co-authored-by: GunChleoc <fios@foramnagaidhlig.net>
Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

config/application.rb

@@ -54,6 +54,7 @@ module Mastodon
     # All translations from config/locales/*.rb,yml are auto loaded.
     # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
     config.i18n.available_locales = [
+      :af,
       :ar,
       :ast,
       :bg,
@@ -76,6 +77,7 @@ module Mastodon
       :fi,
       :fr,
       :ga,
+      :gd,
       :gl,
       :he,
       :hi,
@@ -110,6 +112,7 @@ module Mastodon
       :ru,
       :sa,
       :sc,
+      :si,
       :sk,
       :sl,
       :sq,