Upgraded AdMob SDK to version 7.59

Breaking changes

• Plugin now requires App Id from AdMob to be placed in the Extensibility Configuration

Example:

{
    "plugin": {
        "url": "GITHUB_URL",
        "variables": [
            {
                "name": "APP_ID_ANDROID",
                "value": "ca-app-pub-5814248574003790~3877756530"
            },
            {
                "name": "APP_ID_IOS",
                "value": "ca-app-pub-5814248574003790~8307956131"
            }
        ]
    }
}