Integrate new tooling into main branch CI

[horazont]

Summary

In order to reduce the manual load on the editor, it is important that steps run automatically as far as reasonably possible.

Work proposal

On pushes to the main branch:

• uses Devise a robust, transactional system for "publishing" repository versions #1236 to trigger the existing tooling for archiving and sending emails (tools/archive.py and tools/send-updates.py)
• uses Create tool to facilitate automatic creation of git tags for new XEP releases #1238 to create and push git tags