Add banner for Incognito Mode

(cherry picked from commit cf39ae0000)

app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferencesHelper.kt

@@ -275,7 +275,7 @@ class PreferencesHelper(val context: Context) {
 
     fun sortChapterByAscendingOrDescending() = prefs.getInt(Keys.defaultChapterSortByAscendingOrDescending, Manga.SORT_DESC)
 
-    fun incognitoMode() = prefs.getBoolean(Keys.incognitoMode, false)
+    fun incognitoMode() = flowPrefs.getBoolean(Keys.incognitoMode, false)
 
     fun setChapterSettingsDefault(manga: Manga) {
         prefs.edit {

app/src/main/java/eu/kanade/tachiyomi/ui/main/MainActivity.kt

@@ -234,6 +234,10 @@ class MainActivity : BaseActivity<MainActivityBinding>() {
         preferences.downloadedOnly()
             .asImmediateFlow { binding.downloadedOnly.isVisible = it }
             .launchIn(scope)
+
+        preferences.incognitoMode()
+            .asImmediateFlow { binding.incognitoMode.isVisible = it }
+            .launchIn(scope)
     }
 
     override fun onNewIntent(intent: Intent) {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPresenter.kt

@@ -470,7 +470,7 @@ class ReaderPresenter(
      * Saves this [chapter] last read history.
      */
     private fun saveChapterHistory(chapter: ReaderChapter) {
-        if (!preferences.incognitoMode()) {
+        if (!preferences.incognitoMode().get()) {
             val history = History.create(chapter.chapter).apply { last_read = Date().time }
             db.updateHistoryLastRead(history).asRxCompletable()
                 .onErrorComplete()