Add check for "TRADEMARKS"

CNCF Projects have to xfer their trademark over to the foundation.

There's no easy way to check for this but @amye were chatting that we may have a new policy in CNCF to have a "TRADEMARKS" file at the root of the repo that essentially links to https://www.linuxfoundation.org/trademark-usage/ after we confirm the paperwork is sent our way

No files or tests are named. First confirm whether the CNCF policy and required TRADEMARKS file are finalized, then inspect the existing repository health checks to find where this check belongs. Done means reliably detecting the root-level file and verifying that it links to the Linux Foundation trademark-usage page.

Written by the indexing model from the issue text.