Feature CORS Proxy

Hello all.

I have implemented something like proxy for iOS wkwebview.
It works exactly the same way as `ionic server` with proxies does.

I need your help in order to test the feature.

Installation:
1. ionic cordova plugin rm cordova-plugin-ionic-webview
1. ionic cordova plugin add https://github.com/troyanskiy/cordova-plugin-ionic-webview.git

Add proxies list:
That need to be added into the `config.xml`
```xml

```

For future releases and if people will need that i'm planing also implement ssl pinning on the proxy requests, add capacitor support (will need to check that) and maybe something else.

If you will find any bug related to the proxy feel free to open an issue here https://github.com/troyanskiy/cordova-plugin-ionic-webview/issues

Thanks!