Feature Request: add a config option for 'max-batch-size'

We are using the batching feature in a mono-repo setup with 25 Devs. Our pipelines are running between 20-90 minutes.

We run quite often in a situation where the batches get bigger and bigger because Marge waits until all pipelines of assigned MRs have finished. But when a new MR is assigned to Marge and she is currently waiting for a pipeline to finish, this newly assigned MR will also in the "batch space" and Marge waits also for this new assigned pipeline/MR.

Quite often Marge waits until evening, when no new MR gets assigned because the Devs go home. Then we have 15-30 MR in this huge batch and you have to wait until the next day to get a MR merged via Marge.

To defuse this situation it would be greate to configure the maximum batch size. When the batch has reached this maximum Marge should not add more MR or wait for more pipelines to finish and just takes these mergeable MR in the batch.