Resolve "Login screen setup (without backend)"

Closes #19 (closed)

frontend/core/src/com/game/tankwars/model/MenuHeader.java

+package com.game.tankwars.model;
+
+import com.badlogic.gdx.graphics.Texture;
+
+public class MenuHeader {
+
+    private final Texture texture;
+
+    public MenuHeader() {
+        texture = new Texture("main-menu-welcome-box.png");
+    }
+
+    public Texture getTexture() {
+        return  texture;
+    }
+
+}