Add Steam controller input manager and integrate with Steam API

scripts/steam_integration.gd

@@ -1,13 +1,34 @@
 class_name SteamIntegration
 extends Node
 
-var app_id: String = "3575090"
+var app_id: String         = "3575090"
+var is_on_steam_deck: bool = false
+var is_online: bool        = false
+var has_bought_game: bool  = false
 
 
 func _init() -> void:
-	OS.set_environment("STEAM_APP_ID", app_id)
-	OS.set_environment("STEAM_GAME_ID", app_id)
+	OS.set_environment("SteamAppId", app_id)
+	OS.set_environment("SteamGameId", app_id)
 
 
 func _ready() -> void:
-	pass
+	Steam.steamInit()
+	Steam.enableDeviceCallbacks()
+	SteamControllerInput.init()
+	var is_running := Steam.isSteamRunning()
+
+	if !is_running:
+		print("Steam is not running.")
+		return
+
+	print("Steam is running.")
+
+	is_on_steam_deck = Steam.isSteamRunningOnSteamDeck()
+	is_online = Steam.loggedOn()
+	has_bought_game = Steam.isSubscribed()
+
+	if not has_bought_game:
+		print("You have not bought the game.")
+		get_tree().quit(69)
+