Add NativeMailerHandler from Monolog

[Mardl]

Add handler for NativeMailerLog from Issue #191.
Example to use in your own loggers.json handler entry point

{
    "id": "import.logger.factory.handler.native.mail.log",
    "formatter": {
        "id": "import.logger.factory.formatter.line",
        "params": {
            "format": "[%datetime%] %channel%.%level_name%: %message% %context% %extra%",
            "date-format": "Y-m-d H:i:s",
            "allow-inline-line-breaks": true,
            "ignore-empty-context-and-extra": true
        }
    },
    "params": {
        "to": [
            "[email protected]"
        ],
        "subject": "Something Went Wrong",
        "from": "[email protected]",
        "level": "error",
        "bubble": true,
        "maxColumnWidth": 500
    }
}