continued inventory saving (missing things will be created in an issue asap)

src/de/miaurizius/jgame2d/data/DataStorage.java

@@ -0,0 +1,28 @@
+package de.miaurizius.jgame2d.data;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.List;
+
+public class DataStorage implements Serializable {
+
+    // PLAYER STATS
+    int level;
+    int maxLife;
+    int life;
+    int maxMana;
+    int strength;
+    int dexterity;
+    int attack;
+    int defense;
+    int exp;
+    int nextLevelExp;
+    int coins;
+    int worldX, worldY;
+
+    // PLAYER INVENTORY
+    List<String> itemNames = new ArrayList<>();
+    List<Integer> itemAmounts = new ArrayList<>();
+
+
+}