ebiten: add an API to change window title bar color mode

[hajimehoshi]

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• OpenBSD
• Android
• iOS
• Nintendo Switch
• PlayStation 5
• Xbox
• Web Browsers

What feature would you like to be added?

I propose an API to chnage the color mode for the window title bar

func SetWindowTitleBarColorMode(colorMode ColorMode)

ColorMode will be introduced at #3386

Why is this needed?

Some applications want to have a dark colored window title bar.

Related: #3386, #3381