Function application 

pub fn application<State, Message, Theme, Renderer>(
    boot: impl BootFn<State, Message>,
    update: impl UpdateFn<State, Message>,
    view: impl for<'a> ViewFn<'a, State, Message, Theme, Renderer>,
) -> Application<impl Program<State = State, Message = Message, Theme = Theme>>
where
    State: Send + 'static,
    Message: Send + 'static,
    Theme: Base,
    Renderer: Renderer,