added cost amount to items

added Shop UI
added Shop.cs
 * you now can buy items and you lose the cost when bought
 * shop is scrollable

added comments in Inventory.cs, InventorySlot.cs, InventoryUI.cs
now showing description when hovering over items in shop or inventory

Assets/Scripts/HoverManager.cs

@@ -0,0 +1,48 @@
+using System;
+using TMPro;
+using UnityEngine;
+
+public class HoverManager : MonoBehaviour {
+    public TextMeshProUGUI descriptionText;
+    public RectTransform descriptionHoverBackground;
+
+    public static Action<string, Vector2> onMouseHover;
+    public static Action onMouseExit;
+
+    private void OnEnable() {
+        onMouseHover += ShowDescription;
+        onMouseExit += HideDescription;
+    }
+
+    private void OnDisable() {
+        onMouseHover -= ShowDescription;
+        onMouseExit -= HideDescription;
+    }
+
+    private void Start() {
+        HideDescription();
+    }
+
+    /**
+     * Show the description Text at the mouse position
+     */
+    private void ShowDescription(string description, Vector2 mousePos) {
+        descriptionText.text = description;
+        descriptionHoverBackground.sizeDelta =
+            new Vector2(descriptionText.preferredWidth > 200 ? 200 : descriptionText.preferredWidth,
+                descriptionText.preferredHeight);
+        
+        descriptionHoverBackground.gameObject.SetActive(true);
+        float descBgX = descriptionHoverBackground.sizeDelta.x;
+        descriptionHoverBackground.transform.position =
+            new Vector2(mousePos.x + (descBgX / 2) + (descBgX / 16), mousePos.y);
+    }
+
+    /**
+     * Hide the description Text
+     */
+    private void HideDescription() {
+        descriptionText.text = default;
+        descriptionHoverBackground.gameObject.SetActive(false);
+    }
+}