Publish .well-known endpoints

[tcpipuk]

To avoid unnecessary SRV lookups, a vanity domain needs to publish a /.well-known/matrix/server endpoint to direct homeservers to itself.

Many self-hosters will also want to serve their vanity domain from HTTPS/443 instead of the default port 8448, which would also require delegation.

Finally, as this homeserver doesn't have any users of its own, it would be healthy to serve the /.well-known/matrix/support endpoint, so users can see who the admin/moderation details for this domain.

Both of these can be achieved with static files, but it would be helpful to set these details in the same config file alongside the vanity domain, especially when using the docker image so everything is served from one container.