Add Deathlink

[EvelynTSMG]

Would resolve #48.

[EvelynTSMG]

At the moment, completely and utterly untested. I ran out of time for today!

[EvelynTSMG]

After a bit testing in a limited environment, this is ready for review.
The code isn't the cleanest, but so long as it works it can be like this for now.
We can improve it after a refactor targeting hooks.cs and archipelago.cs.

Known issues:

• Dying to Doom does not trigger the Post-KO code, hence avoiding sending a deathlink.

[Andrewki44]

After some iterative testing last week this seemed pretty successful.

Cannot be merged until fahrenheit-crew/fahrenheit#138 is complete.

Would also like to see an associated Apworld PR for this, but not necessary for it to be merged. The option works independently on client side as-is.

[EvelynTSMG]

A successful merge would increase the urgency of #206, as it would cause queue doubled deathlinks when one is received.

[Andrewki44]

Should we consider that blocking in that case?

[EvelynTSMG]

I believe the issue is rare enough to not need to be considered blocking, but do as you will.

[EvelynTSMG]

Necessary changes