complete page_3 and setup game menu tabs

core/game_menu/game_menu.gd

@@ -0,0 +1,22 @@
+extends Control
+
+@onready var tabs: Array[GameMenuTab] = [$%Tab1, $%Tab2, $%Tab3]
+@onready var pages: Array[Control] = [$%Page1, $%Page2, $%Page3]
+
+func _ready() -> void:
+	for tab: GameMenuTab in tabs:
+		tab.on_tab_selected.connect(_on_tab_pressed)
+	
+	tabs[0].select()
+
+func _on_tab_pressed(index: int):
+	for page in pages:
+		page.hide()
+		
+	for tab in tabs:
+		if tab.index == index:
+			tab.select()
+		else:
+			tab.deselect()
+		
+	pages[index].show()