Add labels to alert output

[martialblog]

• This adds more detail to the alerts

Fixes #72

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

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cmd/alert_test.go:89

• The JSON label for 'alertname' in this alert has changed to 'TLS'. Please verify that this change is intentional and aligns with the intended alert naming for consistency.

+\_ [CRITICAL] [BlackboxTLS] - Job: [blackbox] on Instance: [https://localhost:443] is firing - value: -6065338.00 - {"alertname":"TLS","instance":"https://localhost:443","job":"blackbox","severity":"critical"}