refactor: utilize NPCType

src/main/java/uulm/teamname/marvelous/gamelibrary/entities/Character.java

@@ -46,7 +46,7 @@ public class Character extends Entity {
         super(id, position);
         solid = false;
         opaque = true;
-        if(id.type == EntityType.NPC && id.id == 2) {
+        if(id.type == EntityType.NPC && id.id == NPCType.Thanos.getID()) {
             solid = true; //characters cannot walk into thanos
         }
         this.name = name;

src/main/java/uulm/teamname/marvelous/gamelibrary/entities/NPCType.java

@@ -2,7 +2,17 @@ package uulm.teamname.marvelous.gamelibrary.entities;
 
 /** Specifies the type of an {@link NPC}. */
 public enum NPCType {
-    Goose,
-    Stan,
-    Thanos
+    Goose(0),
+    Stan(1),
+    Thanos(2);
+
+    private final int id;
+
+    NPCType(int id) {
+        this.id = id;
+    }
+
+    public int getID() {
+        return id;
+    }
 }