An R-multiverse topic is a list of packages that share a subject matter domain (for example, packages that fit Bayesian models).
To contribute a new package to an existing topic, add the topic URL to the URL field of the DESCRIPTION file (example here), then create a new GitHub/GitLab release of the package.
To contribute a new topic, submit a pull request to https://github.com/r-multiverse/topics to add a new text file (with no file extension) whose name is the topic name and whose contents describe the topic. An automated workflow periodically creates HTML pages from these text files.