You can have the documentation site hosted on a custom domain with help of rewrites
This feature has a slight disadvantage - it's not possible to have customdomain.com/docs/ yet. Instead one can have customdomain.com/SLUG/docs.
But this should be fixed soon.
Replace all SLUGs here with the one you created while creating site in hyperdocs dashboard
We can use any service to rewrite all the routes to our documentation site from the custom domain.
Let's use Vercel here
Create a new repo
Add your custom domain/subdomain to that repo
Add a vercel.json file with the following content: