Allow retry Parameter below 30s

Hello there,

would it be possible in the future to make the "retry" parameter configurable under 30s.

I would like to create a notification that arrives every 5s within about 1min. This would be much more helpful in getting a user's attention in a short window of time than sending a notification every 30s over a long period of time.

I would really appreciate it if you could provide a solution to this in the future. Perhaps you could limit the general number of notifications so that your API is not overloaded.

Many thanks and best regards