Add language: Scottish Gaelic (#7864)

* Create messages.po

* Update app.config.js

* Update lingui.config.js

* Update dates.ts

* Update helpers.ts

* Update i18n.ts

* Update i18n.web.ts

* Update languages.ts

src/components/hooks/dates.ts

@@ -20,6 +20,7 @@ import {
   eu,
   fi,
   fr,
+  gd,
   gl,
   hi,
   hu,
@@ -64,6 +65,7 @@ const locales: Record<AppLanguage, Locale | undefined> = {
   fi,
   fr,
   ga: undefined,
+  gd,
   gl,
   hi,
   hu,