Proposal: WebView.SetIcon

[dark-pink]

Add new method SetIcon to set window icon image.

Type and parameter IconKind allows to specify usage of icon (if supported).

// IconKind is used to specify usage of icon.
type IconKind int

const (
	IconKindDefault = IconKind(iota)
	IconKindSmaller
)

type WebView interface {
	// SetIcon updates the icon of the native window. Must be called from the UI
	// thread.
	SetIcon(icon image.Image, kind IconKind)

	// ...
}

Pull request: https://github.com/webview/webview_go/pull/47