This allows us to introduce a platform-specific `Action` to both `iced_native`
and `iced_web` and remove the `Clipboard` from `Application::update` to maintain
purity.
Additionally, this should let us implement further actions to let users query
and modify the shell environment (e.g. window, clipboard, and more!)
A `Message` should represent an application event (e.g. user
interactions, command results, subscription results...). Therefore, it
should always consist of pure, cloneable data.
