Add status types spam complained and subscription changed

Editor assessment

The scope is admirably specific, naming the Postmark webhook parser, and the subject does enumerate which status types were added, but the missing separators make 'spam complained and subscription changed' read as prose rather than as the identifiers 'spam', 'complained', and 'subscriptionchanged', so the reader must already know Postmark's status vocabulary. Feat is correct. No body explains how these statuses map to internal ones or why they matter for users of the integration. Hygiene is otherwise fine: imperative, no junk, no trailing period. Precise content, sloppy presentation, and therefore acceptable rather than good.