Summary

We should publish the specifications documents to ReadTheDocs.

Motivation

We currently publish docs to the internal documentation site, but they are not versioned (by date or by specification version, for instance) or accessible to external contributors.
We can publish our docs to ReadTheDocs and get versioned documentation that is publicly accessible.
An alternative to ReadTheDocs is to use GitHub Actions to publish to a GitHub Pages website, but that would require GitHub App credentials to push to the branch, and would not enable versioning.

Notes

We can use mkdocs to publish our markdown docs to our project.

Acceptance Criteria

Docs are automatically published to "latest" on ReadTheDocs, as well as for tagged releases.