[feat] API on settings::Window to configure enabled buttons via winit::WindowBuilder:: set_enabled_buttons

[leoshimo]

I'd like to extend settings::Window API to have a value to configure winit::WindowBuilder::set_enabled_buttons

This is the API I'd like to wire up in iced's winit:
https://github.com/iced-rs/winit/blob/c52db2045d0a2f1b8d9923870de1d4ab1994146e/src/window.rs#L264-L267

It seems like I can update winit/src/settings.rs chunk below to call set_enabled_buttons:
https://github.com/iced-rs/iced/blob/master/winit/src/settings.rs#L129-L137

Would this be the right option to add? Curious if we should use the winit::window::WindowButtons directly as part of Iced's API, or introduce an indirection like iced_core::window::Level or iced_winit::settings::PlatformSpecific and mapping to WindowButton

[leoshimo]

PR for iterating + discussion: #2035