main menu image, custom style
	modified:   LibreSTR/LibreSTR.cbp
	new file:   LibreSTR/LibreSTRStyle.cpp
	new file:   LibreSTR/LibreSTRStyle.h
	modified:   LibreSTR/MainMenu.cpp
	modified:   LibreSTR/MainMenu.h
	modified:   LibreSTR/main.cpp
	new file:   assets/mainmenu_image.png