In the (beer) brewing sector the unit of hectoliter is used constantly. In the VolumeUnit enum that unit is implemented, but is missing in the VolumeFlowUnit enum.

It would be great if this unit could be implemented, since all machines we build use this as the base unit for volume flow.

If no one has the time to implement this feature, I would consider implementing it myself and therefore create a pull request once I implemented it. I'm just a total noob to this, since I have never contributed to any repo other then my own.