Version: up to 0.3e @ Minecraft 1.16.5

Comparators and stockpile switches cannot read the contents of deployers. I don't know yet if this is intended.

Example: I'm trying to automate a Farmer's delight Cooking pot using Create. The specific goal of the deployer is to right-click the pot with a bowl to fill it with ratatouille. However, this doesn't work if the deployer contains more than one bowl, as there aren't any slots left in its 1-item inventory. So I was trying to put bowls using a hopper that I can lock if the deployer already contains one. And as I said, I haven't yet found any ways to detect if the deployer holds something.

I might be able to implement this and PR if it helps.

Closing in favor of #1144, which I didn't see while searching.