refactor(transport): make widgets focusable

crates/tek_sequencer/src/arranger.rs

@@ -15,8 +15,12 @@ pub struct Arranger {
     pub mode:     ArrangerViewMode,
     /// Slot for modal dialog displayed on top of app.
     pub modal:    Option<Box<dyn ExitableComponent>>,
+    /// Whether the arranger is currently focused
+    pub focused:  bool
 }
 
+focusable!(Arranger (focused));
+
 impl Arranger {
     pub fn new (name: &str) -> Self {
         Self {
@@ -25,7 +29,8 @@ impl Arranger {
             selected: ArrangerFocus::Clip(0, 0),
             scenes:   vec![],
             tracks:   vec![],
-            modal:    None
+            modal:    None,
+            focused:  false
         }
     }
     pub fn activate (&mut self) {