First off, thank you for thinking so highly of FreeRTOS Wrappers that you want to contribute to it! When I started this project, I never imaginged there would be so many folks interested in it. I am very happy this project has been useful to so many.
The preferred bug reporting channel is via Github Issues
Regarding contributing to the FreeRTOS source, (i.e. Emailing files, push requests, etc.), right now, and for the forseeable future, you will need transfer all copyrights to the original author of FreeRTOS wrappers for any work that you want considered for inclusion. This requirement shouldn''t limit you in any way. The code is released under the MIT License, so you always have access to it. You can also create as many derivative works as you want from it. But to have your code considered for inclusion back into the official code base, you need to provide a copyright assignment of that code.