Heya,
as far as I’m aware we don’t have community addons yet.
Integration is not the word you’re searching for, as integrations live in our codebase (like LDAP does) - you’re searching for “package(s)” and “addon”. Addons basically can extend Zammad with further features - that’s correct.
We currently have no real developer documentation we can share.
The only leading topic for this is: Custom plugin to parse ticket content but you already found that one. 