Log through a GameLog autoload instead of print()

GameLog.debug() prints only in debug builds, and GameLog.warning() reports
problems such as unexpected server data or failed downloads.

QRWindow.gd

@@ -19,7 +19,7 @@ func _ready() -> void:
 	var url: String = Settings.default_path + "/search"
 	qr_code_rect.data = url
 	url_label.text = qr_code_rect.data
-	print("QR code generated for: ", url)
+	GameLog.debug("QR code generated for: ", url)
 
 func open() -> void:
 	super()