Add skins "aventure", "nature" and "items"

assets/skins/items_1.png

assets/skins/items_2.png

assets/skins/items_3.png

assets/skins/items_4.png

assets/skins/items_5.png

assets/skins/items_6.png

assets/skins/items_7.png

assets/skins/items_8.png

assets/skins/items_found.png

assets/skins/items_unknown.png

assets/skins/nature_1.png

assets/skins/nature_2.png

assets/skins/nature_3.png

assets/skins/nature_4.png

assets/skins/nature_5.png

assets/skins/nature_6.png

assets/skins/nature_7.png

assets/skins/nature_8.png

assets/skins/nature_found.png

assets/skins/nature_unknown.png