Clarifications on @capacitor/filesystem Directory enum

## Clarifications

### Plugin
@capacitor/filesystem

### Description
I am working with `@capacitor/filesystem` package and struggle with picking directories for specific purposes. The package has the following enum defined:

```
export declare enum Directory {
/**
* The Documents directory
* On iOS it's the app's documents directory.
* Use this directory to store user-generated content.
* On Android it's the Public Documents folder, so it's accessible from other apps.
* It's not accesible on Android 10 unless the app enables legacy External Storage
* by adding `android:requestLegacyExternalStorage="true"` in the `application` tag
* in the `AndroidManifest.xml`.
* It's not accesible on Android 11 or newer.
*
* @since 1.0.0
*/
Documents = "DOCUMENTS",
/**
* The Data directory
* On iOS it will use the Documents directory.
* On Android it's the directory holding application files.
* Files will be deleted when the application is uninstalled.
*
* @since 1.0.0
*/
Data = "DATA",
/**
* The Library directory
* On iOS it will use the Library directory.
* On Android it's the directory holding application files.
* Files will be deleted when the application is uninstalled.
*
* @since 1.1.0
*/
Library = "LIBRARY",
/**
* The Cache directory
* Can be deleted in cases of low memory, so use this directory to write app-specific files
* that your app can re-create easily.
*
* @since 1.0.0
*/
Cache = "CACHE",
/**
* The external directory
* On iOS it will use the Documents directory
* On Android it's the directory on the primary shared/external
* storage device where the application can place persistent files it owns.
* These files are internal to the applications, and not typically visible
* to the user as media.
* Files will be deleted when the application is uninstalled.
*
* @since 1.0.0
*/
External = "EXTERNAL",
/**
* The external storage directory
* On iOS it will use the Documents directory
* On Android it's the primary shared/external storage directory.
* It's not accesible on Android 10 unless the app enables legacy External Storage
* by adding `android:requestLegacyExternalStorage="true"` in the `application` tag
* in the `AndroidManifest.xml`.
* It's not accesible on Android 11 or newer.
*
* @since 1.0.0
*/
ExternalStorage = "EXTERNAL_STORAGE"
}
```

From what it says, Android 11 or newer can only utilize Data, Library, Cache, and External folders.

---

From my understanding, I can use and I need to store the following types of content:

- `Library/Data/External`: System files (database files)
- `Data/External`: User-uploaded data (images, videos, files, uploaded to the application)
- `?`: Downloads from my application (backup export)

---

So, I have the following questions:

- Which directories should I use to store these types of data and why?
- Also, what is meant by shared/external? SD card?
- What's the difference between `External` and `ExternalStorage`? Both were introduced at the same time (since 1.0.0). Do they end up pointing to different locations?

---

For external downloads from my application (backup export) I tried to use `Documents` directory (`Download` folder in it, specified via a separate `path` parameter), and it seems to be working for me, even though my phone is `Android 12 (Funtouch OS_10.5)`. I am not sure if it will also be working for other users on other systems.

I also tried checking out [Android documentation](https://developer.android.com/training/data-storage) on that topic, but it seems to not be bound to these enum values.