Emagged fishing capsules can create deep water (#90798)

## About The Pull Request

Alongside lava and plasma, emagged fishing capsules can now create 3x3
areas of deep water.
Unfortunately "deep ocean" does not have a unique fishing loot pool at
the moment, but maybe one day.

## Why It's Good For The Game

It was a discord request from a head admin and it seemed reasonably
funny. These tiles are significantly less dangerous than lava but
perhaps more flavourful and also effect terrain in a different way.
People will avoid lava because it basically kills you, but this is a
trap they might be more tempted to chase you across (to their
detriment).

## Changelog

🆑
add: Emagging a fishing spot pod from the black market can create pools
of water deep enough to drown people in.
/🆑

code/modules/mining/shelters.dm

@@ -172,3 +172,11 @@
 	description = "A small 2x2 puddle of not-safe-for-live plasma. You can catch lava loops and arctic chrabs here."
 	radial_icon = "plasma"
 	safe = FALSE
+
+/datum/map_template/shelter/fishing/depths
+	name = "Deep Ocean Fishing Spot"
+	shelter_id = "fishing_depths"
+	mappath = "_maps/templates/fishing_depths.dmm"
+	description = "A 3x3 pool of deep water, enough that it's tiring to wade across. You can catch ocean fish here."
+	radial_icon = "depths"
+	safe = FALSE