This is not a question I've encountered before but this depends on a few things. If you are using GitHub for your repository it is possible to get a copy of these comments via the API. I am not aware of a solution that organizes these into any type of content management system but it would be possible to write a script that would pull these details from each pull request and then add them to a document or use another API to post them to a platform like MediaWiki or WordPress.

My searching led me to this page which provides some more information on using the GitHub API to gather this data.