Add eojthebrave as a co-maintainer

I'm currently an active maintainer for both the user_guide, and user_guide_tests projects. This theme was originally created to facilitate running the tests in user_guide_tests, and to add as a demonstration theme for downloading and installing in documentation in the actual guide. As someone working on keeping both of those projects going it would be nice to also be able to make commits to this project.

As an example, I'm currently working on updating the user guide content for Drupal 10. But doing so requires updating this project for Drupal 10 first. So if possible it would be great to be able to help maintain this theme. Thanks!