hreflangs for Volto 16

[erral]

• I signed and returned the Plone Contributor Agreement, and received and accepted an invitation to join a team in the Plone GitHub organization.
• I verified there aren't other open pull requests for the same change.
• I followed the guidelines in Contributing to Volto.
• I succesfully ran code linting checks on my changes locally.
• I succesfully ran unit tests on my changes locally.
• I succesfully ran acceptance tests on my changes locally.
• If needed, I added new tests for my changes.
• If needed, I added documentation for my changes, either in the Storybook or narrative documentation.
• I included a change log entry in my commits.

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The same as #6603 for Volto 16.x

[erral]

I think we can disregard the documentation tests here, right @stevepiercy ?

[iFlameing]

Same as previous everything is good :)

[stevepiercy]

@erral yes, we can ignore the RTD failures. We don't maintain 16.0 docs, and it we only recently supported RTD on main.

[davisagli]

@stevepiercy Is there any way to disable the RTD builds for PRs targeting the 16.x.x and 17.x.x branches?

[stevepiercy]

@davisagli not that I could find. We could try removing the .readthedocs.yml file, since RTD complains that it lacks the sphinx.config key, or we could try adding that key and see if it stops complaining about that requirement and exits as it should. Let's try the latter. I can try later tonight, or you're welcome to take a stab at it.

[davisagli]

@stevepiercy Ok. I don't think it's worth a large effort.

[stevepiercy]

To amend my last comment, deleting the .readthedocs.yaml file will still cause a failure.

https://readthedocs.org/projects/plone-registry/builds/26947396/

I think I can put a logical if in the workflow file.

https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/using-conditions-to-control-job-execution

If that doesn't have the desired effect, I'll try adding this snippet:

sphinx:
  # Path to your Sphinx configuration file.
  configuration: docs/src/conf.py

It won't handle the @plone/registry failure though.

[stevepiercy]

See related PRs.

• Split RTD PR preview builds between Volto and plone/registry #6617
• Use build.commands to disable RTD build on 16.x.x #6618
• Use build.commands to disable RTD build on 17.x.x #6619