Add explicit ReadTheDocs configuration.

[bdice]

Description

ReadTheDocs shared the following announcement:

We are announcing the deprecation of projects using Sphinx or MkDocs without an explicit configuration in their .readthedocs.yaml file. After January 20, 2025, Read the Docs will require explicit configuration for all Sphinx and MkDocs projects.

This adds the explicit key required by the above.

Checklist:

• I am familiar with the Contributing Guidelines.
• I agree with the terms of the Contributor Agreement.
• My code follows the code style guideline of this project.

[bdice]

I will admin-merge this because CI is passing and this is similar to the change in glotzerlab/gsd#410.

[joaander]

@bdice I failed to get the notification because I am not a maintainer of signac-docs on readthedocs. Could you invite me?

[bdice]

@joaander I think you're already there? The signac repo maps to signac-core on ReadTheDocs, and the signac-docs repo maps to signac on ReadTheDocs. I see all 5 signac-related ReadTheDocs projects (signac, signac-core, signac-flow, signac-dashboard, and synced_collections) on your user profile: https://app.readthedocs.org/profiles/joaander/?page=2

Let me know if something needs changed.

[joaander]

Thanks for clarifying how the repository names map to readthedocs projects.

[bdice]

No problem. We chose that mapping so that the top-level project mapped onto https://docs.signac.io/en/latest/ was named "signac" for the framework as a whole.