AK: Add reverse iterator as member

Author: https://github.com/guerinoni
Commit: 0aed2f0f86
Pull-request: https://github.com/SerenityOS/serenity/pull/12741
Reviewed-by: https://github.com/IdanHo
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/linusg

AK/Vector.h

@@ -704,6 +704,11 @@ public:
     Iterator end() { return Iterator::end(*this); }
     ReverseIterator rend() { return ReverseIterator::rend(*this); }
 
+    ALWAYS_INLINE constexpr auto in_reverse()
+    {
+        return ReverseWrapper::in_reverse(*this);
+    }
+
     template<typename TUnaryPredicate>
     ConstIterator find_if(TUnaryPredicate&& finder) const
     {