fix: focus handler typings

Typings did not allow passing a function taking `setFocused` to addEventListener

Fixing by using the same typings as in `onlineManager.ts`, tweaked to allow default Window.Event behavior

Author: fmauquie

src/core/focusManager.ts

@@ -12,12 +12,12 @@ class FocusManager extends Subscribable {
   }
 
   setEventListener(
-    setup: (onFocus: () => void) => (focused?: boolean) => void
+    setup: (setFocused: (focused: boolean | Event) => void) => () => void
   ): void {
     if (this.removeEventListener) {
       this.removeEventListener()
     }
-    this.removeEventListener = setup((focused?: boolean) => {
+    this.removeEventListener = setup((focused) => {
       if (typeof focused === 'boolean') {
         this.setFocused(focused)
       } else {