added dialog start radius and background by time in cutscenes

resources/dialogue/sample_dialogues.json

@@ -160,7 +160,8 @@
           "speaker": "Ghost",
           "portrait": "resources/ghost_avatar.png",
           "text": "Some memories never fade.",
-          "durationMs": 2600
+          "durationMs": 2600,
+          "background": "resources/loading.png"
         }
       ]
     }