Add documentation for Foxconn RU

This MR adds documentation for using the Foxconn RU with OAI, as it piques the interest of some in the community. Note that this RU is not continuously tested with OAI L1. Additionally, we have observed throughput degradation in OAI versions beyond tag 2024.w30, and the issue is under investigation. For now, we are providing documentation based on what we have tested in our lab.