animation: Accept ms as u32

Less boilerplate elsewhere.

src/layout/workspace.rs

@@ -401,7 +401,7 @@ impl<W: LayoutElement> Workspace<W> {
         self.view_offset_anim = Some(Animation::new(
             self.view_offset as f64,
             new_view_offset as f64,
-            Duration::from_millis(250),
+            250,
         ));
     }