Add Assistant content URLs

This is surfaced in recents on Pixel devices for example.
Docs: https://developer.android.com/guide/app-actions/assistant-sharing

Co-authored-by: Jays2Kings <Jays2Kings@users.noreply.github.com>

app/src/main/java/eu/kanade/presentation/util/Navigator.kt

@@ -18,6 +18,10 @@ interface Tab : cafe.adriel.voyager.navigator.tab.Tab {
     suspend fun onReselect(navigator: Navigator) {}
 }
 
+interface AssistContentScreen {
+    fun onProvideAssistUrl(): String?
+}
+
 @Composable
 fun DefaultNavigatorScreenTransition(navigator: Navigator) {
     val slideDistance = rememberSlideDistance()