Add openapi.yaml to versioned folders in gh-pages

[m-mohr]

Publish the OpenAPI document (yaml and maybe even json) via gh-pages, so that they can be accessed directly without GH dependency in the URL.

So it should be https://api.openeo.org/1.2.0/openapi.yaml instead of https://raw.githubusercontent.com/Open-EO/openeo-api/refs/tags/1.2.0/openapi.yaml

Ideally also do it for 1.0.0 and 1.1.0.