Set up schema URL publishing, similar to what the specification repository used to do.

[jsuereth]

Previosuly

https://github.com/open-telemetry/opentelemetry-specification/blob/main/.github/workflows/publish-schemas.yml

Now

Opentelemetry.io can directly consume our release and pull schema files from a "mounted module", see:

https://github.com/open-telemetry/opentelemetry.io/blob/main/hugo.yaml#L194C14-L194C14

And

open-telemetry/opentelemetry.io#2907

[jsuereth]

Closing in favor of open-telemetry/opentelemetry.io#2721