Rename storage file

Renaming storage file to something more specific prevent conflicts
with data filenames used by
other similar programs.

src/main/java/tsundere/task/Storage.java

@@ -15,7 +15,7 @@
  */
 public class Storage {
 
-    private static final String FILEPATH = "./data/data.txt";
+    private static final String FILEPATH = "./data/tsunderedata.txt";
 
     /**
      * Initializes Storage.