LibJS: Implement Intl.getCanonicalLocales

Author: https://github.com/trflynn89
Commit: 38d29a40dc
Pull-request: https://github.com/SerenityOS/serenity/pull/9599
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/davidot
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Runtime/Intl/Intl.h

@@ -17,6 +17,9 @@ public:
     explicit Intl(GlobalObject&);
     virtual void initialize(GlobalObject&) override;
     virtual ~Intl() override = default;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(get_canonical_locales);
 };
 
 }