Find suitable anchor view for SnackBar

This will fix the SnackBar position if BottomNav or FAB is visible.

Fix #5163
Fix #5135

app/src/main/java/com/topjohnwu/magisk/arch/BaseUIActivity.kt

@@ -35,6 +35,7 @@ abstract class BaseUIActivity<VM : BaseViewModel, Binding : ViewDataBinding> :
 
     open val navHostId: Int = 0
     open val snackbarView get() = binding.root
+    open val snackbarAnchorView: View? get() = null
 
     init {
         val theme = Config.darkTheme

app/src/main/java/com/topjohnwu/magisk/arch/BaseUIFragment.kt

@@ -22,6 +22,7 @@ abstract class BaseUIFragment<VM : BaseViewModel, Binding : ViewDataBinding> :
 
     override val viewRoot: View get() = binding.root
     private val navigation get() = activity.navigation
+    open val snackbarAnchorView: View? get() = null
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)