单一py文件拆分为py文件模块，功能完成

assets/common.py

@@ -0,0 +1,13 @@
+import os
+import json
+
+def saveJSON(data, filename):
+    with open(filename, 'w', encoding='utf-8') as f:
+        json.dump(data, f, ensure_ascii=False, indent=4)
+
+def readJSON(filename):
+    with open(filename, 'r', encoding='utf-8') as f:
+        return json.load(f)
+
+def fileExists(filename):
+    return os.path.exists(filename)