Add comment to explain what LocalBackButtonVisibility is intended for.

Author: dturner

app/src/main/java/com/example/nav3recipes/scenes/listdetail/ListDetailScene.kt

@@ -27,7 +27,6 @@ import androidx.compose.material3.adaptive.currentWindowAdaptiveInfo
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.compositionLocalOf
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.navigation3.runtime.NavEntry
@@ -94,6 +93,11 @@ class ListDetailScene<T : Any>(
     }
 }
 
+/**
+ * This `CompositionLocal` can be used by a detail `NavEntry` to decide whether to display
+ * a back button. Default is `true`. It is set to `false` for a detail `NavEntry` when being
+ * displayed in a `ListDetailScene`.
+ */
 val LocalBackButtonVisibility = compositionLocalOf{ true }
 
 @Composable