feat: add support for Chat Webhooks messages

[maelgangloff]

Describe your changes

Webhooks allow sending messages in many instant messaging software (Mattermost, Rocket.Chat, ...). In addition to email alerts, it may be useful to add support for these messages by Webhook.

Type of change

• [x] New feature (non-breaking change which adds functionality)

Checklist before requesting a review

• [x] Commit names follow the Conventional Commits convention
• [x] I have checked the entire code before submitting it
• [ ] I have updated the documentation related to my commits
• [x] My code does not generate errors

[maelgangloff]

Thanks for your review @vinceh121 :tada: