Fade in the web view

[sindresorhus]

It would be nice to fade in the web view when the page has loaded. Right now, it just shows a gray background on the first start until the page loads.

Plash/Plash/AppDelegate.swift

Lines 139 to 143 in a6aa255

	// TODO: Add a callback to `loadURL` when it's done loading instead.
	// TODO: Fade in the web view.
	delay(seconds: 1) {
	self.desktopWindow.contentView?.isHidden = false
	}

Here are some fade utilities: https://github.com/sindresorhus/Gifski/blob/5602861e7cf1970dcf19442e546e70d74cc30d58/Gifski/util.swift#L1397-L1428