Expose a way to determine if the rate limit is already hit?

If this exists already perhaps you can help me identify how to do it. I'm looking for a way to detect whether a particular key will overflow in the next call. Digging into the source it looks like it would be using this method
within_rate_limit? but would need to not increment the counter

```
def next_within_rate_limit?
ExcessFlow::GlobalMutex.locked(lock_key: configuration.lock_key) do
cleanup_stale_counters

if current_requests < configuration.limit
true
else
false
end
end
end
end
```

The big difference is it wouldn't call the "bump_counter" method.

Start by locating the existing within_rate_limit? entry point and tracing cleanup_stale_counters, current_requests, and bump_counter. Confirm how the rate-limit state is checked, then add a non-incrementing way to determine whether the next call would exceed the configured limit and verify that the counter remains unchanged.

Written by the indexing model from the issue text.