Add webhook notifications

[Cgboal]

This PR adds the ability to configure webhook notifications via the evilginx config file.

By setting webhook_url and webhook_param, it is possible to extract params from proxied requests and forward them to the webhook URL.

This was done to allow evilginx to inform gophish when links have been clicked by retrieving the rid tracking parameter used by gophish and forwarding it to the gophish url as defined in webhook_param.

[noname1007]

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