adapt to new Task struct instead of Command

src/app.rs

@@ -17,7 +17,7 @@ use chrono::{NaiveDate, Months, Utc, Days};
 use std::path;
 use iced::{
     Alignment,
-    Command,
+    Task,
     Element,
     Length,
     widget::{
@@ -72,7 +72,7 @@ impl CalendarApp {
         app
 	}
 
-    pub fn update(&mut self, message: Message) -> Command<Message> {
+    pub fn update(&mut self, message: Message) -> Task<Message> {
         match message {
             Message::PrevWeek => {
                 self.view_date = self.view_date - Days::new(7);
@@ -96,7 +96,7 @@ impl CalendarApp {
                 self.controls.mode = Some(mode);
             }
         }
-        Command::none()
+        Task::none()
     }
 
     pub fn view(&self) -> Element<Message> {