http3 support

[Motophan]

So the way the labels are implamented the following labels will not work to enable http3 support

client -> http/3 -> cf -> LE traefik -> http/2

--experimental.http3=true
--entrypoints.name.enablehttp3=true

but I get "command traefik error: field not found, node: enableHTTP3"
I believe this is because we use outdated yaml cli for traefik?

I switched to traefik:latest and pulled the latest image to no avail.

Possible relevant discussions
traefik/traefik#5514
traefik/traefik#7724