Set app icon

[tonsky]

TODO: Check AWT & JavaFX

Preliminary:

Window::setIcon(File)

Window::setIcon(byte[])

• Windows
• Linux
• macOS

[i10416]

Which image fomat should SetIcon(File) function support?

( Windows native api(hIcon) seems to support only .ico format. )

[tonsky]

We were thinking of whatever native platform expects. That would mean ico for Windows, icns for macOS, not sure what (png?) for Linux

[tonsky]

Will be followed up by #135