add Task and Action for changing a window title

runtime/src/window.rs

@@ -73,6 +73,9 @@ pub enum Action {
     /// Get the current [`Mode`] of the window.
     GetMode(Id, oneshot::Sender<Mode>),
 
+    /// Change the title of the window.
+    ChangeTitle(Id, String),
+
     /// Toggle the window to maximized or back
     ToggleMaximize(Id),
 
@@ -368,6 +371,11 @@ pub fn change_level<T>(id: Id, level: Level) -> Task<T> {
     task::effect(crate::Action::Window(Action::ChangeLevel(id, level)))
 }
 
+/// Changes the title of the window.
+pub fn change_title<T>(id: Id, title: String) -> Task<T> {
+    task::effect(crate::Action::Window(Action::ChangeTitle(id, title)))
+}
+
 /// Show the [system menu] at cursor position.
 ///
 /// [system menu]: https://en.wikipedia.org/wiki/Common_menus_in_Microsoft_Windows#System_menu