Change api endpoint to be /api instead of /openapi

[rouault]

Overview

Cf

• OGC API Features - Part 1 (https://docs.ogc.org/is/17-069r4/17-069r4.html#_api_definition_path_rootapi_link) para 7.3.1, permission 1: "it MAY be hosted as a sub-resource to the base path of the API, for example, at path /api"

• OGC API Common Part 1 (https://docs.ogc.org/is/19-072/19-072.html#_6f30c0b2-ff4c-4c38-8d51-bd124f4b76cc) para 9.2, Recommandation 15.A: "The server SHOULD support the HTTP GET operation on the URI {root}/api."

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[tomkralidis]

@rouault is /openapi breaking any functionality (given the recommendations and permissions [but not requirements] from OGC API - Features / OGC API - Common)?