Support equal co-authorship on personal posts

Is your feature request related to a problem? Please describe.

DEV supports co-authors for posts published under organization accounts, but personal posts do not provide an equivalent way to represent two or more people as equal authors.

This can be limiting for projects, hackathons, DEV Challenges, open-source work, and other collaborations where two individuals genuinely contributed to the same work.

Currently, one person may have to publish the post under their account while the other contributor is only mentioned in the content.

Describe the solution you'd like

Allow authors to add one or more co-authors when publishing a personal post.

A co-authored post could:

• Display all authors prominently.
• Appear on each author's profile.
• Attribute the post to all participating authors.
• Allow each author to receive relevant engagement notifications.
• Clearly distinguish co-authored posts from posts written by a single author.

The existing organization co-author functionality could potentially serve as a starting point, while adapting it for personal accounts.

Describe alternatives you've considered

• Publishing under an organization account.
• Mentioning collaborators in the post body.
• Tagging collaborators in the comments.
• Having one person publish while the other is only credited informally.

These approaches provide credit, but they do not represent equal authorship accurately.

Additional context

I encountered this limitation while writing about a project I built collaboratively:

https://dev.to/dj29/5-devto-features-i-wish-existed-3-im-genuinely-relieved-they-dont-3b8n

For collaborative projects, particularly hackathons and DEV Challenges, the distinction between "primary author + contributor" and "equal co-authors" can be meaningful.