Add entity proximity modifier

[Forstride]

Basically the same as the block proximity modifier, but for entities (Magma Cubes, Blazes, Snowmen, etc.). Although I'm not sure if/how spreading will be able to work with that. Could just work with block proximity and check if a tagged entity is in the block.

[lostopkk]

I was thinking about creating an issue to see if the player was in a very cold place, another player could stay close as if they were hugging each other to warm up their bodies.

[Forstride]

Ehhh I mean, it's not a bad idea, but it doesn't really feel like something obvious that people would expect or rely on. Plus for it to really make sense, it would have to apply to pretty much any entity that would give off ambient body heat (Villagers, farm animals, etc.), not just players. And at that point it would probably get a bit unbalanced.

I really only want to have this for entities where it's obvious that they give off heat/cold and could reasonably do so in larger radius than only standing right next to them.