Adds format=json support to world/topic (#50446)

random fact: the original game banners from erro used a custom url decoder. It wasn't until a year or two in to me being host that i caught on and fixed this.

code/datums/world_topic.dm

@@ -27,11 +27,16 @@
 
 /datum/world_topic/proc/TryRun(list/input)
 	key_valid = config && (CONFIG_GET(string/comms_key) == input["key"])
-	if(require_comms_key && !key_valid)
-		return "Bad Key"
 	input -= "key"
-	. = Run(input)
-	if(islist(.))
+	if(require_comms_key && !key_valid)
+		. = "Bad Key"
+		if (input["format"] == "json")
+			. = list("error" = .)
+	else
+		. = Run(input)
+	if (input["format"] == "json")
+		. = json_encode(.)
+	else if(islist(.))
 		. = list2params(.)
 
 /datum/world_topic/proc/Run(list/input)