Adds a chat message for fishing in a chasm with a normal and rescue hook (#83781)

## About The Pull Request

Title, warns you if you have anormal hook and gives you a heads up it
might work otherwise.

## Why It's Good For The Game

Everyone knows 'fish in chasm to get body', but not many people know
'you can ONLY use the rescue hook to get body'. This clarifies that! It
reduces misinformation and confusion.

## Changelog

🆑
qol: Adds a chat message for fishing in a chasm with a normal and rescue
hook, to clarify that only rescue hooks can drag up corpses.
/🆑

code/modules/fishing/sources/_fish_source.dm

@@ -69,6 +69,10 @@ GLOBAL_LIST_INIT(specific_fish_icons, zebra_typecacheof(list(
 /datum/fish_source/proc/reason_we_cant_fish(obj/item/fishing_rod/rod, mob/fisherman, atom/parent)
 	return rod.reason_we_cant_fish(src)
 
+/// Called below above proc, in case the fishing source has anything to do that isn't denial
+/datum/fish_source/proc/on_start_fishing(obj/item/fishing_rod/rod, mob/fisherman, atom/parent)
+	return
+
 /**
  * Calculates the difficulty of the minigame:
  *

code/modules/fishing/sources/source_types.dm

@@ -196,6 +196,13 @@
 
 	fishing_difficulty = FISHING_DEFAULT_DIFFICULTY + 5
 
+/datum/fish_source/chasm/on_start_fishing(obj/item/fishing_rod/rod, mob/fisherman, atom/parent)
+	. = ..()
+	if(istype(rod.hook, /obj/item/fishing_hook/rescue))
+		to_chat(fisherman, span_notice("The rescue hook falls straight down the chasm! Hopefully it catches a corpse."))
+		return
+	to_chat(fisherman, span_danger("Your fishing hook makes a soft 'thud' noise as it gets stuck on the wall of the chasm. It doesn't look like it's going to catch much of anything, except maybe some detritus."))
+
 /datum/fish_source/chasm/roll_reward(obj/item/fishing_rod/rod, mob/fisherman)
 	var/rolled_reward = ..()
 
@@ -204,6 +211,8 @@
 
 	return rod.hook.chasm_detritus_type
 
+/datum/fish_source/chasm
+
 /datum/fish_source/lavaland
 	catalog_description = "Lava vents"
 	background = "background_lavaland"