Suggestion for charts: Rate calculation

Suggestion for charts: Rate calculation

This would be useful for time series. Imagine I am plotting something like the number of bytes sent or received, DNS queries, errors, whatever numeric quantity.

Now, depending on the number of buckets if, for example, I am using bars I see the total number of events per bucket. But it would be great to represent it in events per second, minute or whatever unit is convenient.

I see that the line chart does some kind of averaging but it can be still a bit confusing.

## Why?
In many contexts we use units such as events per second, bytes per second, queries per second or per minute... Charts would be easier to understand and to interpret when correlating with other tools.

## Your Environment

* Graylog Version: Graylog 7.0.0beta 3 but applicable to 6.x as well.
* OpenSearch Version:
* MongoDB Version:
* Operating System:
* Browser version: