Move the trademark policy from the wiki to this repo
The current trademark policy is located in the wiki: https://wiki.archlinux.org/title/DeveloperWiki:TrademarkPolicy
One issue that comes to mind is that the trademark policy is not a "service agreement", it won't be shown to users upon registration via Keycloak, which was the original purpose of this repo. But the descriptions of the project (which seem to define its scope) are already inconsistent, the published documents at https://terms.archlinux.org/ call it "Arch Linux Terms" or "Arch Linux legal documentation". The issue can be solved by defining the scope of the repo properly.