Use static hide timeout for all reader setting previews

The default timeout of "notistack" is 5s by default, however, this makes it more clear and also prevents any behaviour changes in the future, in case the default timeout gets changed

src/modules/reader/screens/Reader.tsx

@@ -300,10 +300,14 @@ const BaseReader = ({
             return;
         }
 
+        const HIDE_PREVIEW_TIMEOUT = 5000;
+
         const didReadingModeChange = JSON.stringify(readingMode) !== JSON.stringify(previousReadingMode.current);
         const showReadingModePreview = shouldShowReadingModePreview && didReadingModeChange;
         if (showReadingModePreview) {
-            makeToast(t(READING_MODE_VALUE_TO_DISPLAY_DATA[readingMode.value].title as TranslationKey));
+            makeToast(t(READING_MODE_VALUE_TO_DISPLAY_DATA[readingMode.value].title as TranslationKey), {
+                autoHideDuration: HIDE_PREVIEW_TIMEOUT,
+            });
         }
         previousReadingMode.current = readingMode;
 
@@ -314,7 +318,7 @@ const BaseReader = ({
         if (showTapZoneLayoutPreview) {
             setShowPreview(true);
             if (isInitialPreview.current) {
-                setTimeout(() => setShowPreview(false), 5000);
+                setTimeout(() => setShowPreview(false), HIDE_PREVIEW_TIMEOUT);
             }
         }
         previousTapZoneLayout.current = tapZoneLayout;