Fullscreen and Windowed mode added!

Hey guys,

In this update, we added the feature to shift between windowed and fullscreen mode in Summer in Springtime's desktop builds. The game starts out in windowed mode, and you can enter and exit fullscreen mode upon starting or loading a game, and selecting the Fullscreen/Windowed option in the In-game menu. Our games have always been in fullscreen mode and some players were wondering about playing in a window instead, maybe because their monitors are ultra wide or something. The wrapper we use doesn't have the maximize window option for some reason. We've also sync'd in some added bug fixes and features from our other VN to this one.