Custom Backgrounds update!!!

This update adds possibility to change game backgrounds to ones from your hard drive. They should be 820x460 and have png extension (other extensions were not tested) You can access that in settings menu under S key while in main menu (with burning game logo)

CHANGELOG:

- added settings menu and possibility to add custom bg's

- shortened time of text at the beggining

- fixed desktop icon (no more default godot engine one)