Support for knowing remaining limit

[srijanmehrotra]

There are scenarios where the client is interested in knowing the remaining limit. This information is usually passed back to client as part of response headers.
Can we add a method like
long getRemainingLimitInCurrentWindow(String key) in es.moki.ratelimitj.core.limiter.request.RequestRateLimiter
This will definitely help in utilising this library in web filters.
Please advise I am interested in taking this up.