[Feature]: Docs suggest there is email feature

[nbbn]

Guidelines

• I agree to follow this project's Contributing Guidelines.

Description

According to: https://appsilon.github.io/data.validator/#working-example
there should be an option to sent email from data.validator. I think it is not the case.

Problem

Docs tell about emailing user when there is failed validation. It is not a part of this package and this is not supported.

Proposed Solution

Add notification feature (to Slack it is quite easy, to email there is always a lot of configuration and problems with deliverability).

Alternatives Considered

Remove this from docs or add well-visible disclaimer.