added getter for the JSON string to ParseException

Author: iSnow

src/main/java/io/api/etherscan/error/ParseException.java

@@ -13,4 +13,8 @@ public ParseException(String message, Throwable cause, String json) {
         super(message, cause);
         this.json = json;
     }
+
+    public String getJson() {
+        return json;
+    }
 }