Add documentation for notification reports

[piksel]

Currently there is no mention of --notification-report in the docs.
Add documentation for --notification-report to arguments, and a separate page with some sample templates for common scenarios:

• Generic JSON report/logs
• Increase/decrease verbosity (conditional sending)
• Include new data props .Subject and .Host

Update: The docs are added, but they don't mention the data props, nor the built in JSON template.

ref #1203

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[simskij]

These docs seem to me like they're in good enough condition to close this issue.

[piksel]

Actually, there are still two points that I would like to add to the docs, sorry for forgetting about this issue.