Add basic author information to topic data

[oplik0]

Related to #12192

Adds a bit of author metadata to topicData so that themes can correctly display DiscussionForumPosting structured data.

[nodebb-misty]

💡 Friendly Note

This pull request was made against the develop branch, which is reserved for commits destined for a minor or major release.If your commits simply fixes a bug, please rebase this PR against the master instead.

• patch releases — bug fixes only
• minor releases — new features, enhancements, and bug fixes
• major releases — breaking changes, including all of the above

Thanks!