Unable to load a local URL or html file in Corodva iOS with inAppBrowser

# Bug Report

## Problem

### What is expected to happen?

### What does actually happen?

I have recently upgraded to Cordova InAppBrowser plugin to 3.2.0 which uses wkwebview to render HTML content. I have always been able to load local HTML file by using the following the code:

```
cordova.InAppBrowser.open(
'cdvfile://localhost/bundle/www/assets/index.html',
'_blank',
);
```

However, wkwebview doesn't support 'cdvfile' so I tried using the relative file as below

```
cordova.InAppBrowser.open(
'assets/index.html',
'_blank',
);
```

This approach is not working either. The inAppBrowser opens and shows HTML Error 403: forbidden. After I close the browser, all the local files like IMG becomes unavailable and browser console [Error] Failed to load resource: the server responded with a status of 403 (Forbidden). I don't understand why closing browser cause other local files become accessible.

## Information

### Command or Code

### Environment, Platform, Device

I m using the cordova-plugin-wkwebview-engine plugin which forces to use WKwebview. here are the configs

```

```

### Version information

Cordova ios: 5.1.1
ios: 13.4
Cordova: 9.0

## Checklist

- [ ] I searched for existing GitHub issues
- [ ] I updated all Cordova tooling to most recent version
- [ ] I included all the necessary information above

Start by reproducing the issue with cordova.InAppBrowser.open using both the cdvfile URL and the relative assets/index.html URL under the supplied WKWebView configuration. Inspect the InAppBrowser and WKWebView handling of local URLs; done means the HTML file and its local resources load without 403 errors and remain accessible after closing the browser.

Written by the indexing model from the issue text.