I believe you can do this multiple ways, GitHub allows you to create Teams and Projects and then it also allows you to add Topics to repositories.

1) If you don't want to have access control on your repositories you can simply create a project and link it multiple repositories to it.

2) In a similar vein, another approach without access control is adding a topics to your repositories and then searching them in the GitHub search bar using *topic: your-topic".

3) Finally, if you need to have access controls or permissions on your repositories you can create teams and assign that team repositories.

I am not a professional or corporate user, so please forgive me if any of this not 100% accurate.