Add Ye arc battlefield backgrounds

data/scenarios/014_cangting_pursuit.json

@@ -172,6 +172,7 @@
     "cells": [[1, 3], [1, 4], [1, 5], [2, 2], [2, 3], [2, 4], [2, 5], [2, 6], [3, 2], [3, 3], [3, 4], [3, 5]]
   },
   "map": {
+    "background": "res://art/backgrounds/cangting_pursuit.png",
     "width": 17,
     "height": 11,
     "terrain": [

data/scenarios/015_ye_campaign.json

@@ -177,6 +177,7 @@
     "cells": [[1, 3], [1, 4], [1, 5], [2, 2], [2, 3], [2, 4], [2, 5], [2, 6], [3, 2], [3, 3], [3, 4], [3, 5], [3, 6]]
   },
   "map": {
+    "background": "res://art/backgrounds/ye_outer_defense.png",
     "width": 18,
     "height": 11,
     "terrain": [

data/scenarios/016_ye_siege.json

@@ -172,6 +172,7 @@
     "cells": [[1, 3], [1, 4], [1, 5], [2, 2], [2, 3], [2, 4], [2, 5], [2, 6], [3, 2], [3, 3], [3, 4], [3, 5], [3, 6]]
   },
   "map": {
+    "background": "res://art/backgrounds/ye_inner_gate.png",
     "width": 18,
     "height": 11,
     "terrain": [

data/scenarios/017_ye_surrender.json

@@ -172,6 +172,7 @@
     "cells": [[1, 3], [1, 4], [1, 5], [2, 2], [2, 3], [2, 4], [2, 5], [2, 6], [3, 2], [3, 3], [3, 4], [3, 5], [3, 6]]
   },
   "map": {
+    "background": "res://art/backgrounds/ye_palace_road.png",
     "width": 18,
     "height": 11,
     "terrain": [