Use app name for page download folder and use manga title subfolders (closes #4684)

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

@@ -559,7 +559,8 @@ class ReaderPresenter(
         val destDir = File(
             Environment.getExternalStorageDirectory().absolutePath +
                 File.separator + Environment.DIRECTORY_PICTURES +
-                File.separator + "Tachiyomi"
+                File.separator + context.getString(R.string.app_name) +
+                File.separator + manga.title
         )
 
         // Copy file in background.