All issues requesting peer review use the peer-review tag (with a dash, like this group). People can also optionally focus the review they are looking for with tags such as code-review, ux-review, etc.
If you are requesting peer review of a project, you should open a new issue dedicated to the review. State what you are most looking for in the review, and any reviewer will post responses in that issue. The category should be task, and don't forget to tag it peer-review!