Fixed SonarQube issue in TiledLevelLoader.
Fixed SonarQube issue in TiledLevelLoader.

The issue as reported in SonarQube stated that `int.Parse` should
always be called with an `ICultureProvider` instance to prevent
culture-specific issues. Since the text to be parsed is in machine-
readable format, the culture provider used is `CultureInfo.InvariantCulture`.

thijser/ARGAME,thijser/ARGAME,thijser/ARGAME