Miner is_mining field

[foxmadnes]

Hi!

I'm working on a small mod I have not released, and I wanted to count the number of actively mining miners at any given point. I noticed that crafters have a shared is_crafting field, so I'm wondering if we can add a similar field/API for all the different miners. I imagine this could be helpful for other mods in the same way is_crafting is likely helpful.

I suppose I might be able to deduce it based on the electricity draw (and might try that in a bit), but that seemed very involved for answering what felt like a quick question about the entity.

[curiosity]

Why mess around with electricity draw if you can just check the status?

And then is_crafting doesn't work like that. It shows if the machine is in a middle of a craft, not its activity.