option for outline ONLY when entity is not visible

[slovinsqui]

make the outline render only when the entity is not visible due to obstructions, instead of the outline being there all the time

[n0rbyt3]

This will be hard to implement since the mod works in another way. It applies the outline to all rendered mobs independant to the player.

There are also some limitations: What happens to players in spectator or creative mode?